From 65ffe83468dc979ac080f3951e49620fa8d561cd Mon Sep 17 00:00:00 2001
From: water111 <48171810+water111@users.noreply.github.com>
Date: Fri, 5 Mar 2021 18:48:01 -0500
Subject: [PATCH] [Decompiler] Decompile `let` (#309)

* test

* fix bug

* fix tests for let

* missing formatting fix
---
 decompiler/CMakeLists.txt                     |    1 +
 decompiler/IR2/Env.cpp                        |   24 +-
 decompiler/IR2/Env.h                          |    6 +
 decompiler/IR2/Form.cpp                       |  336 +++--
 decompiler/IR2/Form.h                         |  134 +-
 decompiler/IR2/FormExpressionAnalysis.cpp     |    5 +-
 decompiler/ObjectFile/ObjectFileDB.h          |    1 +
 decompiler/ObjectFile/ObjectFileDB_IR2.cpp    |   22 +
 decompiler/analysis/insert_lets.cpp           |  342 +++++
 decompiler/analysis/insert_lets.h             |   21 +
 decompiler/config.cpp                         |    1 +
 decompiler/config.h                           |    1 +
 decompiler/config/jak1_ntsc_black_label.jsonc |    1 +
 test/decompiler/FormRegressionTest.cpp        |    5 +-
 test/decompiler/reference/gcommon_REF.gc      | 1129 ++++++++---------
 test/decompiler/test_FormExpressionBuild.cpp  |  392 +++---
 .../test_FormExpressionBuildLong.cpp          |  796 ++++++------
 test/decompiler/test_gkernel_decomp.cpp       |  727 ++++++-----
 test/decompiler/test_math_decomp.cpp          |    6 +-
 test/offline/offline_test_main.cpp            |   17 +-
 20 files changed, 2312 insertions(+), 1655 deletions(-)
 create mode 100644 decompiler/analysis/insert_lets.cpp
 create mode 100644 decompiler/analysis/insert_lets.h

diff --git a/decompiler/CMakeLists.txt b/decompiler/CMakeLists.txt
index f1b1253a1..c30f88629 100644
--- a/decompiler/CMakeLists.txt
+++ b/decompiler/CMakeLists.txt
@@ -6,6 +6,7 @@ add_library(
         analysis/cfg_builder.cpp
         analysis/expression_build.cpp
         analysis/final_output.cpp
+        analysis/insert_lets.cpp
         analysis/reg_usage.cpp
         analysis/variable_naming.cpp
 
diff --git a/decompiler/IR2/Env.cpp b/decompiler/IR2/Env.cpp
index dbd052f03..51353bbc4 100644
--- a/decompiler/IR2/Env.cpp
+++ b/decompiler/IR2/Env.cpp
@@ -82,6 +82,7 @@ goos::Object Env::get_variable_name(Register reg, int atomic_idx, AccessMode mod
     if (type_kv != m_typehints.end()) {
       for (auto& x : type_kv->second) {
         if (x.reg == reg) {
+          // TODO - redo this!
           return pretty_print::build_list("the-as", x.type_name, lookup_name);
         }
       }
@@ -92,6 +93,19 @@ goos::Object Env::get_variable_name(Register reg, int atomic_idx, AccessMode mod
   }
 }
 
+std::string Env::get_variable_name(const RegisterAccess& access) const {
+  if (access.reg().get_kind() == Reg::FPR || access.reg().get_kind() == Reg::GPR) {
+    std::string lookup_name = m_var_names.lookup(access.reg(), access.idx(), access.mode()).name();
+    auto remapped = m_var_remap.find(lookup_name);
+    if (remapped != m_var_remap.end()) {
+      lookup_name = remapped->second;
+    }
+    return lookup_name;
+  } else {
+    throw std::runtime_error("Cannot store a variable in this reg");
+  }
+}
+
 /*!
  * Update the Env with the result of the type analysis pass.
  */
@@ -167,7 +181,7 @@ std::vector<VariableNames::VarInfo> Env::extract_visible_variables(
   std::vector<VariableNames::VarInfo> entries;
   if (top_level_form) {
     RegAccessSet var_set;
-    top_level_form->collect_vars(var_set);
+    top_level_form->collect_vars(var_set, true);
 
     // we want to sort them for easier reading:
     std::vector<std::pair<RegId, RegisterAccess>> vars;
@@ -243,13 +257,19 @@ goos::Object Env::local_var_type_list(const Form* top_level_form,
         x.reg_id.reg.get_gpr() >= Reg::A0 && x.reg_id.id == 0) {
       continue;
     }
-    count++;
+
     std::string lookup_name = x.name();
     auto remapped = m_var_remap.find(lookup_name);
     if (remapped != m_var_remap.end()) {
       lookup_name = remapped->second;
     }
 
+    if (m_vars_defined_in_let.find(lookup_name) != m_vars_defined_in_let.end()) {
+      continue;
+    }
+
+    count++;
+
     elts.push_back(pretty_print::build_list(lookup_name, x.type.typespec().print()));
   }
   if (count_out) {
diff --git a/decompiler/IR2/Env.h b/decompiler/IR2/Env.h
index 00993bc7b..2d20b8dce 100644
--- a/decompiler/IR2/Env.h
+++ b/decompiler/IR2/Env.h
@@ -43,7 +43,9 @@ class Env {
     return m_reg_use;
   }
 
+  // TODO - remove this.
   goos::Object get_variable_name(Register reg, int atomic_idx, AccessMode mode) const;
+  std::string get_variable_name(const RegisterAccess& access) const;
 
   /*!
    * Get the types in registers _after_ the given operation has completed.
@@ -126,6 +128,8 @@ class Env {
     }
   }
 
+  void set_defined_in_let(const std::string& var) { m_vars_defined_in_let.insert(var); }
+
   LinkedObjectFile* file = nullptr;
   DecompilerTypeSystem* dts = nullptr;
 
@@ -148,5 +152,7 @@ class Env {
   std::unordered_map<int, std::vector<TypeHint>> m_typehints;
   std::unordered_map<std::string, std::string> m_var_remap;
   std::unordered_map<std::string, LabelType> m_label_types;
+
+  std::unordered_set<std::string> m_vars_defined_in_let;
 };
 }  // namespace decompiler
\ No newline at end of file
diff --git a/decompiler/IR2/Form.cpp b/decompiler/IR2/Form.cpp
index 6e9fd1246..e1377d860 100644
--- a/decompiler/IR2/Form.cpp
+++ b/decompiler/IR2/Form.cpp
@@ -120,9 +120,9 @@ void Form::apply_form(const std::function<void(Form*)>& f) {
   }
 }
 
-void Form::collect_vars(RegAccessSet& vars) const {
+void Form::collect_vars(RegAccessSet& vars, bool recursive) const {
   for (auto e : m_elements) {
-    e->collect_vars(vars);
+    e->collect_vars(vars, recursive);
   }
 }
 
@@ -153,7 +153,7 @@ bool SimpleExpressionElement::is_sequence_point() const {
   throw std::runtime_error("Should not check if a SimpleExpressionElement is a sequence point");
 }
 
-void SimpleExpressionElement::collect_vars(RegAccessSet& vars) const {
+void SimpleExpressionElement::collect_vars(RegAccessSet& vars, bool) const {
   m_expr.collect_vars(vars);
 }
 
@@ -177,7 +177,7 @@ void StoreElement::apply(const std::function<void(FormElement*)>& f) {
 
 void StoreElement::apply_form(const std::function<void(Form*)>&) {}
 
-void StoreElement::collect_vars(RegAccessSet& vars) const {
+void StoreElement::collect_vars(RegAccessSet& vars, bool) const {
   return m_op->collect_vars(vars);
 }
 
@@ -239,8 +239,10 @@ void LoadSourceElement::apply_form(const std::function<void(Form*)>& f) {
   m_addr->apply_form(f);
 }
 
-void LoadSourceElement::collect_vars(RegAccessSet& vars) const {
-  m_addr->collect_vars(vars);
+void LoadSourceElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    m_addr->collect_vars(vars, recursive);
+  }
 }
 
 void LoadSourceElement::get_modified_regs(RegSet& regs) const {
@@ -263,7 +265,7 @@ void SimpleAtomElement::apply(const std::function<void(FormElement*)>& f) {
 
 void SimpleAtomElement::apply_form(const std::function<void(Form*)>&) {}
 
-void SimpleAtomElement::collect_vars(RegAccessSet& vars) const {
+void SimpleAtomElement::collect_vars(RegAccessSet& vars, bool) const {
   return m_atom.collect_vars(vars);
 }
 
@@ -301,12 +303,14 @@ bool SetVarElement::is_sequence_point() const {
   return m_is_sequence_point;
 }
 
-void SetVarElement::collect_vars(RegAccessSet& vars) const {
+void SetVarElement::collect_vars(RegAccessSet& vars, bool recursive) const {
   if (m_var_info.is_dead_set || m_var_info.is_dead_false) {
     return;
   }
   vars.insert(m_dst);
-  m_src->collect_vars(vars);
+  if (recursive) {
+    m_src->collect_vars(vars, recursive);
+  }
 }
 
 void SetVarElement::get_modified_regs(RegSet& regs) const {
@@ -350,7 +354,7 @@ void StoreInSymbolElement::apply(const std::function<void(FormElement*)>& f) {
 
 void StoreInSymbolElement::apply_form(const std::function<void(Form*)>&) {}
 
-void StoreInSymbolElement::collect_vars(RegAccessSet& vars) const {
+void StoreInSymbolElement::collect_vars(RegAccessSet& vars, bool) const {
   m_value.collect_vars(vars);
 }
 
@@ -374,7 +378,7 @@ void StoreInPairElement::apply(const std::function<void(FormElement*)>& f) {
 
 void StoreInPairElement::apply_form(const std::function<void(Form*)>&) {}
 
-void StoreInPairElement::collect_vars(RegAccessSet& vars) const {
+void StoreInPairElement::collect_vars(RegAccessSet& vars, bool) const {
   m_value.collect_vars(vars);
   vars.insert(m_pair);
 }
@@ -438,9 +442,11 @@ bool SetFormFormElement::is_sequence_point() const {
   return true;
 }
 
-void SetFormFormElement::collect_vars(RegAccessSet& vars) const {
-  m_src->collect_vars(vars);
-  m_dst->collect_vars(vars);
+void SetFormFormElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    m_src->collect_vars(vars, recursive);
+    m_dst->collect_vars(vars, recursive);
+  }
 }
 
 void SetFormFormElement::get_modified_regs(RegSet& regs) const {
@@ -463,7 +469,7 @@ void AtomicOpElement::apply(const std::function<void(FormElement*)>& f) {
 
 void AtomicOpElement::apply_form(const std::function<void(Form*)>&) {}
 
-void AtomicOpElement::collect_vars(RegAccessSet& vars) const {
+void AtomicOpElement::collect_vars(RegAccessSet& vars, bool) const {
   m_op->collect_vars(vars);
 }
 
@@ -493,7 +499,7 @@ void AsmOpElement::apply(const std::function<void(FormElement*)>& f) {
 
 void AsmOpElement::apply_form(const std::function<void(Form*)>&) {}
 
-void AsmOpElement::collect_vars(RegAccessSet& vars) const {
+void AsmOpElement::collect_vars(RegAccessSet& vars, bool) const {
   m_op->collect_vars(vars);
 }
 
@@ -552,7 +558,7 @@ void ConditionElement::invert() {
   m_kind = get_condition_opposite(m_kind);
 }
 
-void ConditionElement::collect_vars(RegAccessSet& vars) const {
+void ConditionElement::collect_vars(RegAccessSet& vars, bool) const {
   for (auto src : m_src) {
     if (src.has_value() && src->is_var()) {
       vars.insert(src->var());
@@ -580,7 +586,7 @@ void FunctionCallElement::apply(const std::function<void(FormElement*)>& f) {
 
 void FunctionCallElement::apply_form(const std::function<void(Form*)>&) {}
 
-void FunctionCallElement::collect_vars(RegAccessSet& vars) const {
+void FunctionCallElement::collect_vars(RegAccessSet& vars, bool) const {
   return m_op->collect_vars(vars);
 }
 
@@ -610,7 +616,7 @@ void BranchElement::apply(const std::function<void(FormElement*)>& f) {
 
 void BranchElement::apply_form(const std::function<void(Form*)>&) {}
 
-void BranchElement::collect_vars(RegAccessSet& vars) const {
+void BranchElement::collect_vars(RegAccessSet& vars, bool) const {
   return m_op->collect_vars(vars);
 }
 
@@ -628,6 +634,14 @@ void BranchElement::get_modified_regs(RegSet& regs) const {
 // ReturnElement
 /////////////////////////////
 
+ReturnElement::ReturnElement(Form* _return_code, Form* _dead_code)
+    : return_code(_return_code), dead_code(_dead_code) {
+  return_code->parent_element = this;
+  if (dead_code) {
+    dead_code->parent_element = this;
+  }
+}
+
 goos::Object ReturnElement::to_form_internal(const Env& env) const {
   std::vector<goos::Object> forms;
   forms.push_back(pretty_print::to_symbol("return"));
@@ -653,10 +667,12 @@ void ReturnElement::apply_form(const std::function<void(Form*)>& f) {
   }
 }
 
-void ReturnElement::collect_vars(RegAccessSet& vars) const {
-  return_code->collect_vars(vars);
-  if (dead_code) {
-    dead_code->collect_vars(vars);
+void ReturnElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    return_code->collect_vars(vars, recursive);
+    if (dead_code) {
+      dead_code->collect_vars(vars, recursive);
+    }
   }
 }
 
@@ -671,6 +687,12 @@ void ReturnElement::get_modified_regs(RegSet& regs) const {
 // BreakElement
 /////////////////////////////
 
+BreakElement::BreakElement(Form* _return_code, Form* _dead_code)
+    : return_code(_return_code), dead_code(_dead_code) {
+  return_code->parent_element = this;
+  dead_code->parent_element = this;
+}
+
 goos::Object BreakElement::to_form_internal(const Env& env) const {
   std::vector<goos::Object> forms;
   forms.push_back(pretty_print::to_symbol("break"));
@@ -690,9 +712,11 @@ void BreakElement::apply_form(const std::function<void(Form*)>& f) {
   dead_code->apply_form(f);
 }
 
-void BreakElement::collect_vars(RegAccessSet& vars) const {
-  return_code->collect_vars(vars);
-  dead_code->collect_vars(vars);
+void BreakElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    return_code->collect_vars(vars, recursive);
+    dead_code->collect_vars(vars, recursive);
+  }
 }
 
 void BreakElement::get_modified_regs(RegSet& regs) const {
@@ -705,6 +729,15 @@ void BreakElement::get_modified_regs(RegSet& regs) const {
 // CondWithElseElement
 /////////////////////////////
 
+CondWithElseElement::CondWithElseElement(std::vector<Entry> _entries, Form* _else_ir)
+    : entries(std::move(_entries)), else_ir(_else_ir) {
+  for (auto& e : entries) {
+    e.condition->parent_element = this;
+    e.body->parent_element = this;
+  }
+  else_ir->parent_element = this;
+}
+
 goos::Object CondWithElseElement::to_form_internal(const Env& env) const {
   // for now we only turn it into an if statement if both cases won't require a begin at the top
   // level. I think it is more common to write these as a two-case cond instead of an if with begin.
@@ -750,12 +783,14 @@ void CondWithElseElement::apply_form(const std::function<void(Form*)>& f) {
   else_ir->apply_form(f);
 }
 
-void CondWithElseElement::collect_vars(RegAccessSet& vars) const {
-  for (auto& entry : entries) {
-    entry.condition->collect_vars(vars);
-    entry.body->collect_vars(vars);
+void CondWithElseElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    for (auto& entry : entries) {
+      entry.condition->collect_vars(vars, recursive);
+      entry.body->collect_vars(vars, recursive);
+    }
+    else_ir->collect_vars(vars, recursive);
   }
-  else_ir->collect_vars(vars);
 }
 
 void CondWithElseElement::get_modified_regs(RegSet& regs) const {
@@ -779,13 +814,18 @@ void EmptyElement::apply(const std::function<void(FormElement*)>& f) {
 }
 
 void EmptyElement::apply_form(const std::function<void(Form*)>&) {}
-void EmptyElement::collect_vars(RegAccessSet&) const {}
+void EmptyElement::collect_vars(RegAccessSet&, bool) const {}
 void EmptyElement::get_modified_regs(RegSet&) const {}
 
 /////////////////////////////
 // WhileElement
 /////////////////////////////
 
+WhileElement::WhileElement(Form* _condition, Form* _body) : condition(_condition), body(_body) {
+  condition->parent_element = this;
+  body->parent_element = this;
+}
+
 void WhileElement::apply(const std::function<void(FormElement*)>& f) {
   // note - this is done in program order, rather than print order. Not sure if this makes sense.
   f(this);
@@ -806,9 +846,11 @@ void WhileElement::apply_form(const std::function<void(Form*)>& f) {
   condition->apply_form(f);
 }
 
-void WhileElement::collect_vars(RegAccessSet& vars) const {
-  body->collect_vars(vars);
-  condition->collect_vars(vars);
+void WhileElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    body->collect_vars(vars, recursive);
+    condition->collect_vars(vars, recursive);
+  }
 }
 
 void WhileElement::get_modified_regs(RegSet& regs) const {
@@ -820,6 +862,11 @@ void WhileElement::get_modified_regs(RegSet& regs) const {
 // UntilElement
 /////////////////////////////
 
+UntilElement::UntilElement(Form* _condition, Form* _body) : condition(_condition), body(_body) {
+  condition->parent_element = this;
+  body->parent_element = this;
+}
+
 void UntilElement::apply(const std::function<void(FormElement*)>& f) {
   // note - this is done in program order, rather than print order. Not sure if this makes sense.
   f(this);
@@ -840,9 +887,11 @@ void UntilElement::apply_form(const std::function<void(Form*)>& f) {
   condition->apply_form(f);
 }
 
-void UntilElement::collect_vars(RegAccessSet& vars) const {
-  body->collect_vars(vars);
-  condition->collect_vars(vars);
+void UntilElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    body->collect_vars(vars, recursive);
+    condition->collect_vars(vars, recursive);
+  }
 }
 
 void UntilElement::get_modified_regs(RegSet& regs) const {
@@ -854,6 +903,13 @@ void UntilElement::get_modified_regs(RegSet& regs) const {
 // ShortCircuitElement
 /////////////////////////////
 
+ShortCircuitElement::ShortCircuitElement(std::vector<Entry> _entries)
+    : entries(std::move(_entries)) {
+  for (auto& entry : entries) {
+    entry.condition->parent_element = this;
+  }
+}
+
 void ShortCircuitElement::apply(const std::function<void(FormElement*)>& f) {
   f(this);
   for (auto& x : entries) {
@@ -896,10 +952,12 @@ goos::Object ShortCircuitElement::to_form_internal(const Env& env) const {
   return pretty_print::build_list(forms);
 }
 
-void ShortCircuitElement::collect_vars(RegAccessSet& vars) const {
+void ShortCircuitElement::collect_vars(RegAccessSet& vars, bool recursive) const {
   //  vars.insert(final_result);  // todo - this might be unused.
-  for (auto& entry : entries) {
-    entry.condition->collect_vars(vars);
+  if (recursive) {
+    for (auto& entry : entries) {
+      entry.condition->collect_vars(vars, recursive);
+    }
   }
 }
 
@@ -913,6 +971,13 @@ void ShortCircuitElement::get_modified_regs(RegSet& regs) const {
 // CondNoElseElement
 /////////////////////////////
 
+CondNoElseElement::CondNoElseElement(std::vector<Entry> _entries) : entries(std::move(_entries)) {
+  for (auto& entry : entries) {
+    entry.condition->parent_element = this;
+    entry.body->parent_element = this;
+  }
+}
+
 goos::Object CondNoElseElement::to_form_internal(const Env& env) const {
   if (entries.size() == 1 && entries.front().body->is_single_element()) {
     // print as an if statement if we can put the body in a single form.
@@ -958,10 +1023,12 @@ void CondNoElseElement::apply_form(const std::function<void(Form*)>& f) {
   }
 }
 
-void CondNoElseElement::collect_vars(RegAccessSet& vars) const {
-  for (auto& e : entries) {
-    e.condition->collect_vars(vars);
-    e.body->collect_vars(vars);
+void CondNoElseElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    for (auto& e : entries) {
+      e.condition->collect_vars(vars, recursive);
+      e.body->collect_vars(vars, recursive);
+    }
   }
 }
 
@@ -989,7 +1056,7 @@ void AbsElement::apply(const std::function<void(FormElement*)>& f) {
 
 void AbsElement::apply_form(const std::function<void(Form*)>&) {}
 
-void AbsElement::collect_vars(RegAccessSet& vars) const {
+void AbsElement::collect_vars(RegAccessSet& vars, bool) const {
   vars.insert(source);
 }
 
@@ -1021,7 +1088,7 @@ void AshElement::apply(const std::function<void(FormElement*)>& f) {
 
 void AshElement::apply_form(const std::function<void(Form*)>&) {}
 
-void AshElement::collect_vars(RegAccessSet& vars) const {
+void AshElement::collect_vars(RegAccessSet& vars, bool) const {
   vars.insert(value);
   vars.insert(shift_amount);
 }
@@ -1050,8 +1117,10 @@ void TypeOfElement::apply_form(const std::function<void(Form*)>& f) {
   value->apply_form(f);
 }
 
-void TypeOfElement::collect_vars(RegAccessSet& vars) const {
-  value->collect_vars(vars);
+void TypeOfElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    value->collect_vars(vars, recursive);
+  }
 }
 
 void TypeOfElement::get_modified_regs(RegSet&) const {}
@@ -1077,7 +1146,7 @@ void ConditionalMoveFalseElement::apply(const std::function<void(FormElement*)>&
 
 void ConditionalMoveFalseElement::apply_form(const std::function<void(Form*)>&) {}
 
-void ConditionalMoveFalseElement::collect_vars(RegAccessSet& vars) const {
+void ConditionalMoveFalseElement::collect_vars(RegAccessSet& vars, bool) const {
   vars.insert(dest);
   vars.insert(old_value);
   vars.insert(source);
@@ -1112,13 +1181,15 @@ GenericOperator GenericOperator::make_compare(IR2_Condition::Kind kind) {
   return op;
 }
 
-void GenericOperator::collect_vars(RegAccessSet& vars) const {
+void GenericOperator::collect_vars(RegAccessSet& vars, bool recursive) const {
   switch (m_kind) {
     case Kind::FIXED_OPERATOR:
     case Kind::CONDITION_OPERATOR:
       return;
     case Kind::FUNCTION_EXPR:
-      m_function->collect_vars(vars);
+      if (recursive) {
+        m_function->collect_vars(vars, recursive);
+      }
       return;
     default:
       assert(false);
@@ -1324,6 +1395,7 @@ goos::Object GenericElement::to_form_internal(const Env& env) const {
     std::vector<goos::Object> result;
     result.push_back(m_head.to_form(env));
     for (auto x : m_elts) {
+      assert(x->parent_element);
       result.push_back(x->to_form(env));
     }
     return pretty_print::build_list(result);
@@ -1345,10 +1417,12 @@ void GenericElement::apply_form(const std::function<void(Form*)>& f) {
   }
 }
 
-void GenericElement::collect_vars(RegAccessSet& vars) const {
-  m_head.collect_vars(vars);
-  for (auto x : m_elts) {
-    x->collect_vars(vars);
+void GenericElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    m_head.collect_vars(vars, recursive);
+    for (auto x : m_elts) {
+      x->collect_vars(vars, recursive);
+    }
   }
 }
 
@@ -1382,8 +1456,10 @@ void CastElement::apply_form(const std::function<void(Form*)>& f) {
   m_source->apply_form(f);
 }
 
-void CastElement::collect_vars(RegAccessSet& vars) const {
-  m_source->collect_vars(vars);
+void CastElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    m_source->collect_vars(vars, recursive);
+  }
 }
 
 void CastElement::get_modified_regs(RegSet& regs) const {
@@ -1421,14 +1497,16 @@ DerefToken DerefToken::make_expr_placeholder() {
   return x;
 }
 
-void DerefToken::collect_vars(RegAccessSet& vars) const {
+void DerefToken::collect_vars(RegAccessSet& vars, bool recursive) const {
   switch (m_kind) {
     case Kind::INTEGER_CONSTANT:
     case Kind::FIELD_NAME:
     case Kind::EXPRESSION_PLACEHOLDER:
       break;
     case Kind::INTEGER_EXPRESSION:
-      m_expr->collect_vars(vars);
+      if (recursive) {
+        m_expr->collect_vars(vars, recursive);
+      }
       break;
     default:
       assert(false);
@@ -1527,6 +1605,7 @@ DerefElement::DerefElement(Form* base, bool is_addr_of, std::vector<DerefToken>
 }
 
 goos::Object DerefElement::to_form_internal(const Env& env) const {
+  assert(m_base->parent_element);
   std::vector<goos::Object> forms = {pretty_print::to_symbol(m_is_addr_of ? "&->" : "->"),
                                      m_base->to_form(env)};
   for (auto& tok : m_tokens) {
@@ -1550,10 +1629,12 @@ void DerefElement::apply_form(const std::function<void(Form*)>& f) {
   }
 }
 
-void DerefElement::collect_vars(RegAccessSet& vars) const {
-  m_base->collect_vars(vars);
-  for (auto& tok : m_tokens) {
-    tok.collect_vars(vars);
+void DerefElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    m_base->collect_vars(vars, recursive);
+    for (auto& tok : m_tokens) {
+      tok.collect_vars(vars, recursive);
+    }
   }
 }
 
@@ -1564,6 +1645,11 @@ void DerefElement::get_modified_regs(RegSet& regs) const {
   }
 }
 
+void DerefElement::set_base(Form* new_base) {
+  m_base = new_base;
+  m_base->parent_element = this;
+}
+
 /////////////////////////////
 // DynamicMethodAccess
 /////////////////////////////
@@ -1580,7 +1666,7 @@ void DynamicMethodAccess::apply(const std::function<void(FormElement*)>& f) {
 
 void DynamicMethodAccess::apply_form(const std::function<void(Form*)>&) {}
 
-void DynamicMethodAccess::collect_vars(RegAccessSet& vars) const {
+void DynamicMethodAccess::collect_vars(RegAccessSet& vars, bool) const {
   vars.insert(m_source);
 }
 
@@ -1596,7 +1682,13 @@ ArrayFieldAccess::ArrayFieldAccess(RegisterAccess source,
     : m_source(source),
       m_deref_tokens(deref_tokens),
       m_expected_stride(expected_stride),
-      m_constant_offset(constant_offset) {}
+      m_constant_offset(constant_offset) {
+  for (auto& token : m_deref_tokens) {
+    if (token.kind() == DerefToken::Kind::INTEGER_EXPRESSION) {
+      token.expr()->parent_element = this;
+    }
+  }
+}
 
 goos::Object ArrayFieldAccess::to_form_internal(const Env& env) const {
   std::vector<goos::Object> elts;
@@ -1621,10 +1713,12 @@ void ArrayFieldAccess::apply_form(const std::function<void(Form*)>& f) {
   }
 }
 
-void ArrayFieldAccess::collect_vars(RegAccessSet& vars) const {
+void ArrayFieldAccess::collect_vars(RegAccessSet& vars, bool recursive) const {
   vars.insert(m_source);
-  for (auto& tok : m_deref_tokens) {
-    tok.collect_vars(vars);
+  if (recursive) {
+    for (auto& tok : m_deref_tokens) {
+      tok.collect_vars(vars, recursive);
+    }
   }
 }
 
@@ -1657,8 +1751,10 @@ void GetMethodElement::apply_form(const std::function<void(Form*)>& f) {
   m_in->apply_form(f);
 }
 
-void GetMethodElement::collect_vars(RegAccessSet& vars) const {
-  m_in->collect_vars(vars);
+void GetMethodElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  if (recursive) {
+    m_in->collect_vars(vars, recursive);
+  }
 }
 
 void GetMethodElement::get_modified_regs(RegSet& regs) const {
@@ -1677,7 +1773,7 @@ goos::Object StringConstantElement::to_form_internal(const Env&) const {
 
 void StringConstantElement::apply(const std::function<void(FormElement*)>&) {}
 void StringConstantElement::apply_form(const std::function<void(Form*)>&) {}
-void StringConstantElement::collect_vars(RegAccessSet&) const {}
+void StringConstantElement::collect_vars(RegAccessSet&, bool) const {}
 void StringConstantElement::get_modified_regs(RegSet&) const {}
 
 /////////////////////////////
@@ -1691,7 +1787,7 @@ goos::Object ConstantTokenElement::to_form_internal(const Env&) const {
 
 void ConstantTokenElement::apply(const std::function<void(FormElement*)>&) {}
 void ConstantTokenElement::apply_form(const std::function<void(Form*)>&) {}
-void ConstantTokenElement::collect_vars(RegAccessSet&) const {}
+void ConstantTokenElement::collect_vars(RegAccessSet&, bool) const {}
 void ConstantTokenElement::get_modified_regs(RegSet&) const {}
 
 /////////////////////////////
@@ -1702,13 +1798,17 @@ ConstantFloatElement::ConstantFloatElement(float value) : m_value(value) {}
 
 void ConstantFloatElement::apply(const std::function<void(FormElement*)>&) {}
 void ConstantFloatElement::apply_form(const std::function<void(Form*)>&) {}
-void ConstantFloatElement::collect_vars(RegAccessSet&) const {}
+void ConstantFloatElement::collect_vars(RegAccessSet&, bool) const {}
 void ConstantFloatElement::get_modified_regs(RegSet&) const {}
 
 goos::Object ConstantFloatElement::to_form_internal(const Env&) const {
   return pretty_print::float_representation(m_value);
 }
 
+/////////////////////////////
+// StorePlainDeref
+/////////////////////////////
+
 StorePlainDeref::StorePlainDeref(DerefElement* dst,
                                  SimpleExpression expr,
                                  int my_idx,
@@ -1736,15 +1836,19 @@ void StorePlainDeref::apply(const std::function<void(FormElement*)>& f) {
 
 void StorePlainDeref::apply_form(const std::function<void(Form*)>&) {}
 
-void StorePlainDeref::collect_vars(RegAccessSet& vars) const {
+void StorePlainDeref::collect_vars(RegAccessSet& vars, bool recursive) const {
   m_expr.collect_vars(vars);
-  m_dst->collect_vars(vars);
+  m_dst->collect_vars(vars, recursive);
 }
 
 void StorePlainDeref::get_modified_regs(RegSet& regs) const {
   m_dst->get_modified_regs(regs);
 }
 
+/////////////////////////////
+// StoreArrayAccess
+/////////////////////////////
+
 StoreArrayAccess::StoreArrayAccess(ArrayFieldAccess* dst,
                                    SimpleExpression expr,
                                    int my_idx,
@@ -1765,15 +1869,19 @@ void StoreArrayAccess::apply_form(const std::function<void(Form*)>& f) {
   m_dst->apply_form(f);
 }
 
-void StoreArrayAccess::collect_vars(RegAccessSet& vars) const {
+void StoreArrayAccess::collect_vars(RegAccessSet& vars, bool recursive) const {
   m_expr.collect_vars(vars);
-  m_dst->collect_vars(vars);
+  m_dst->collect_vars(vars, recursive);
 }
 
 void StoreArrayAccess::get_modified_regs(RegSet& regs) const {
   m_dst->get_modified_regs(regs);
 }
 
+/////////////////////////////
+// DecompiledDataElement
+/////////////////////////////
+
 DecompiledDataElement::DecompiledDataElement(goos::Object description)
     : m_description(std::move(description)) {}
 
@@ -1787,8 +1895,78 @@ void DecompiledDataElement::apply(const std::function<void(FormElement*)>& f) {
 
 void DecompiledDataElement::apply_form(const std::function<void(Form*)>&) {}
 
-void DecompiledDataElement::collect_vars(RegAccessSet&) const {}
+void DecompiledDataElement::collect_vars(RegAccessSet&, bool) const {}
 
 void DecompiledDataElement::get_modified_regs(RegSet&) const {}
 
+/////////////////////////////
+// LetElement
+/////////////////////////////
+
+LetElement::LetElement(Form* body, bool star) : m_body(body), m_star(star) {
+  m_body->parent_element = this;
+}
+
+void LetElement::add_def(RegisterAccess dst, Form* value) {
+  value->parent_element = this;
+  m_entries.push_back({dst, value});
+}
+
+void LetElement::make_let_star() {
+  m_star = true;
+}
+
+goos::Object LetElement::to_form_internal(const Env& env) const {
+  std::vector<goos::Object> outer = {pretty_print::to_symbol(m_star ? "let*" : "let")};
+
+  std::vector<goos::Object> def_list;
+
+  for (auto& entry : m_entries) {
+    def_list.push_back(pretty_print::build_list(entry.dest.to_form(env), entry.src->to_form(env)));
+  }
+
+  outer.push_back(pretty_print::build_list(def_list));
+  m_body->inline_forms(outer, env);
+  return pretty_print::build_list(outer);
+}
+
+void LetElement::apply(const std::function<void(FormElement*)>& f) {
+  f(this);
+  for (auto& entry : m_entries) {
+    entry.src->apply(f);
+  }
+  m_body->apply(f);
+}
+
+void LetElement::apply_form(const std::function<void(Form*)>& f) {
+  for (auto& entry : m_entries) {
+    entry.src->apply_form(f);
+  }
+  m_body->apply_form(f);
+}
+
+void LetElement::collect_vars(RegAccessSet& vars, bool recursive) const {
+  for (auto& entry : m_entries) {
+    vars.insert(entry.dest);
+  }
+  m_body->collect_vars(vars, recursive);
+}
+
+void LetElement::get_modified_regs(RegSet& regs) const {
+  for (auto& entry : m_entries) {
+    regs.insert(entry.dest.reg());
+  }
+  m_body->get_modified_regs(regs);
+}
+
+void LetElement::add_entry(const Entry& e) {
+  e.src->parent_element = this;
+  m_entries.push_back(e);
+}
+
+void LetElement::set_body(Form* new_body) {
+  m_body = new_body;
+  m_body->parent_element = this;
+}
+
 }  // namespace decompiler
diff --git a/decompiler/IR2/Form.h b/decompiler/IR2/Form.h
index 0526f3e29..92a20ea6a 100644
--- a/decompiler/IR2/Form.h
+++ b/decompiler/IR2/Form.h
@@ -29,7 +29,7 @@ class FormElement {
   virtual void apply(const std::function<void(FormElement*)>& f) = 0;
   virtual void apply_form(const std::function<void(Form*)>& f) = 0;
   virtual bool is_sequence_point() const { return true; }
-  virtual void collect_vars(RegAccessSet& vars) const = 0;
+  virtual void collect_vars(RegAccessSet& vars, bool recursive) const = 0;
   virtual void get_modified_regs(RegSet& regs) const = 0;
   virtual bool active() const;
 
@@ -67,7 +67,7 @@ class SimpleExpressionElement : public FormElement {
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
   bool is_sequence_point() const override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
                          FormStack& stack,
@@ -175,7 +175,7 @@ class StoreElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
 
@@ -195,7 +195,7 @@ class LoadSourceElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   int size() const { return m_size; }
   LoadVarOp::Kind kind() const { return m_kind; }
   const Form* location() const { return m_addr; }
@@ -222,7 +222,7 @@ class SimpleAtomElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   const SimpleAtom& atom() const { return m_atom; }
   void update_from_stack(const Env& env,
@@ -248,7 +248,7 @@ class SetVarElement : public FormElement {
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
   bool is_sequence_point() const override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
   bool active() const override;
@@ -285,7 +285,7 @@ class StoreInSymbolElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
 
@@ -303,7 +303,7 @@ class StoreInPairElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
 
@@ -330,7 +330,7 @@ class SetFormFormElement : public FormElement {
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
   bool is_sequence_point() const override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
 
@@ -356,7 +356,7 @@ class AtomicOpElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
   const AtomicOp* op() const { return m_op; }
@@ -374,7 +374,7 @@ class AsmOpElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
   const AsmOp* op() const { return m_op; }
@@ -403,7 +403,7 @@ class ConditionElement : public FormElement {
   goos::Object to_form_as_condition_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
@@ -440,7 +440,7 @@ class FunctionCallElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
                          FormStack& stack,
@@ -463,7 +463,7 @@ class BranchElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   const BranchOp* op() const { return m_op; }
 
@@ -481,12 +481,11 @@ class ReturnElement : public FormElement {
  public:
   Form* return_code = nullptr;
   Form* dead_code = nullptr;
-  ReturnElement(Form* _return_code, Form* _dead_code)
-      : return_code(_return_code), dead_code(_dead_code) {}
+  ReturnElement(Form* _return_code, Form* _dead_code);
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
 };
@@ -516,12 +515,11 @@ class BreakElement : public FormElement {
  public:
   Form* return_code = nullptr;
   Form* dead_code = nullptr;
-  BreakElement(Form* _return_code, Form* _dead_code)
-      : return_code(_return_code), dead_code(_dead_code) {}
+  BreakElement(Form* _return_code, Form* _dead_code);
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
 };
 
@@ -550,12 +548,11 @@ class CondWithElseElement : public FormElement {
   std::vector<Entry> entries;
   Form* else_ir = nullptr;
   bool already_rewritten = false;
-  CondWithElseElement(std::vector<Entry> _entries, Form* _else_ir)
-      : entries(std::move(_entries)), else_ir(_else_ir) {}
+  CondWithElseElement(std::vector<Entry> _entries, Form* _else_ir);
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
 };
@@ -574,7 +571,7 @@ class EmptyElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
 };
@@ -586,11 +583,11 @@ class EmptyElement : public FormElement {
  */
 class WhileElement : public FormElement {
  public:
-  WhileElement(Form* _condition, Form* _body) : condition(_condition), body(_body) {}
+  WhileElement(Form* _condition, Form* _body);
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
   Form* condition = nullptr;
@@ -605,11 +602,11 @@ class WhileElement : public FormElement {
  */
 class UntilElement : public FormElement {
  public:
-  UntilElement(Form* _condition, Form* _body) : condition(_condition), body(_body) {}
+  UntilElement(Form* _condition, Form* _body);
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
   Form* condition = nullptr;
@@ -640,11 +637,11 @@ class ShortCircuitElement : public FormElement {
   std::optional<bool> used_as_value = std::nullopt;
   bool already_rewritten = false;
 
-  explicit ShortCircuitElement(std::vector<Entry> _entries) : entries(std::move(_entries)) {}
+  explicit ShortCircuitElement(std::vector<Entry> _entries);
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
@@ -672,11 +669,11 @@ class CondNoElseElement : public FormElement {
   bool used_as_value = false;
   bool already_rewritten = false;
   std::vector<Entry> entries;
-  explicit CondNoElseElement(std::vector<Entry> _entries) : entries(std::move(_entries)) {}
+  explicit CondNoElseElement(std::vector<Entry> _entries);
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
   void get_modified_regs(RegSet& regs) const override;
   void update_from_stack(const Env& env,
@@ -695,7 +692,7 @@ class AbsElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
                          FormStack& stack,
@@ -725,7 +722,7 @@ class AshElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
                          FormStack& stack,
@@ -746,7 +743,7 @@ class TypeOfElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
@@ -786,7 +783,7 @@ class ConditionalMoveFalseElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
 };
@@ -804,7 +801,7 @@ class GenericOperator {
   static GenericOperator make_fixed(FixedOperatorKind kind);
   static GenericOperator make_function(Form* value);
   static GenericOperator make_compare(IR2_Condition::Kind kind);
-  void collect_vars(RegAccessSet& vars) const;
+  void collect_vars(RegAccessSet& vars, bool recursive) const;
   goos::Object to_form(const Env& env) const;
   void apply(const std::function<void(FormElement*)>& f);
   void apply_form(const std::function<void(Form*)>& f);
@@ -850,7 +847,7 @@ class GenericElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
                          FormStack& stack,
@@ -873,7 +870,7 @@ class CastElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
@@ -904,7 +901,7 @@ class DerefToken {
   static DerefToken make_field_name(const std::string& name);
   static DerefToken make_expr_placeholder();
 
-  void collect_vars(RegAccessSet& vars) const;
+  void collect_vars(RegAccessSet& vars, bool recursive) const;
   goos::Object to_form(const Env& env) const;
   void apply(const std::function<void(FormElement*)>& f);
   void apply_form(const std::function<void(Form*)>& f);
@@ -937,7 +934,7 @@ class DerefElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
                          FormStack& stack,
@@ -951,7 +948,7 @@ class DerefElement : public FormElement {
   const Form* base() const { return m_base; }
   Form* base() { return m_base; }
   const std::vector<DerefToken>& tokens() const { return m_tokens; }
-  void set_base(Form* new_base) { m_base = new_base; }
+  void set_base(Form* new_base);
 
  private:
   Form* m_base = nullptr;
@@ -965,7 +962,7 @@ class DynamicMethodAccess : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
                          FormStack& stack,
@@ -986,7 +983,7 @@ class ArrayFieldAccess : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
                          FormStack& stack,
@@ -1013,7 +1010,7 @@ class GetMethodElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
@@ -1033,7 +1030,7 @@ class StringConstantElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
@@ -1051,7 +1048,7 @@ class ConstantTokenElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
@@ -1069,7 +1066,7 @@ class ConstantFloatElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void update_from_stack(const Env& env,
                          FormPool& pool,
@@ -1092,7 +1089,7 @@ class StorePlainDeref : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
 
@@ -1113,7 +1110,7 @@ class StoreArrayAccess : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
   void push_to_stack(const Env& env, FormPool& pool, FormStack& stack) override;
 
@@ -1130,13 +1127,41 @@ class DecompiledDataElement : public FormElement {
   goos::Object to_form_internal(const Env& env) const override;
   void apply(const std::function<void(FormElement*)>& f) override;
   void apply_form(const std::function<void(Form*)>& f) override;
-  void collect_vars(RegAccessSet& vars) const override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
   void get_modified_regs(RegSet& regs) const override;
 
  private:
   goos::Object m_description;
 };
 
+class LetElement : public FormElement {
+ public:
+  LetElement(Form* body, bool star = false);
+  void add_def(RegisterAccess dst, Form* value);
+
+  void make_let_star();
+  goos::Object to_form_internal(const Env& env) const override;
+  void apply(const std::function<void(FormElement*)>& f) override;
+  void apply_form(const std::function<void(Form*)>& f) override;
+  void collect_vars(RegAccessSet& vars, bool recursive) const override;
+  void get_modified_regs(RegSet& regs) const override;
+  Form* body() { return m_body; }
+  void set_body(Form* new_body);
+
+  struct Entry {
+    RegisterAccess dest;
+    Form* src = nullptr;
+  };
+  std::vector<Entry> entries() { return m_entries; }
+  void add_entry(const Entry& e);
+  bool is_star() const { return m_star; }
+
+ private:
+  Form* m_body = nullptr;
+  std::vector<Entry> m_entries;
+  bool m_star = false;
+};
+
 /*!
  * A Form is a wrapper around one or more FormElements.
  * This is done for two reasons:
@@ -1186,6 +1211,11 @@ class Form {
 
   const std::vector<FormElement*>& elts() const { return m_elements; }
   std::vector<FormElement*>& elts() { return m_elements; }
+  void claim_all_children() {
+    for (auto elt : elts()) {
+      elt->parent_form = this;
+    }
+  }
 
   void push_back(FormElement* elt) {
     elt->parent_form = this;
@@ -1200,7 +1230,7 @@ class Form {
   void inline_forms(std::vector<goos::Object>& forms, const Env& env) const;
   void apply(const std::function<void(FormElement*)>& f);
   void apply_form(const std::function<void(Form*)>& f);
-  void collect_vars(RegAccessSet& vars) const;
+  void collect_vars(RegAccessSet& vars, bool recursive) const;
 
   void update_children_from_stack(const Env& env,
                                   FormPool& pool,
diff --git a/decompiler/IR2/FormExpressionAnalysis.cpp b/decompiler/IR2/FormExpressionAnalysis.cpp
index 229b72dfa..6312966cc 100644
--- a/decompiler/IR2/FormExpressionAnalysis.cpp
+++ b/decompiler/IR2/FormExpressionAnalysis.cpp
@@ -1348,7 +1348,8 @@ void FunctionCallElement::update_from_stack(const Env& env,
       throw std::runtime_error("Failed to resolve.");
     }
 
-    arg_forms.insert(arg_forms.begin(), unsafe);
+    arg_forms.insert(arg_forms.begin(), mr.maps.forms.at(0));
+
     new_form = pool.alloc_element<GenericElement>(
         GenericOperator::make_function(mr.maps.forms.at(1)), arg_forms);
 
@@ -1750,8 +1751,10 @@ void CondWithElseElement::push_to_stack(const Env& env, FormPool& pool, FormStac
   if (rewrite_as_set && !set_unused) {
     for (auto& entry : entries) {
       rewrite_to_get_var(entry.body->elts(), pool, *last_var, env);
+      entry.body->claim_all_children();
     }
     rewrite_to_get_var(else_ir->elts(), pool, *last_var, env);
+    else_ir->claim_all_children();
   }
 
   // update register info
diff --git a/decompiler/ObjectFile/ObjectFileDB.h b/decompiler/ObjectFile/ObjectFileDB.h
index 562db9506..220550da3 100644
--- a/decompiler/ObjectFile/ObjectFileDB.h
+++ b/decompiler/ObjectFile/ObjectFileDB.h
@@ -75,6 +75,7 @@ class ObjectFileDB {
   void ir2_cfg_build_pass();
   void ir2_store_current_forms();
   void ir2_build_expressions();
+  void ir2_insert_lets();
   void ir2_write_results(const std::string& output_dir);
   std::string ir2_to_file(ObjectFileData& data);
   std::string ir2_function_to_string(ObjectFileData& data, Function& function, int seg);
diff --git a/decompiler/ObjectFile/ObjectFileDB_IR2.cpp b/decompiler/ObjectFile/ObjectFileDB_IR2.cpp
index 7f1c40c3d..633320de8 100644
--- a/decompiler/ObjectFile/ObjectFileDB_IR2.cpp
+++ b/decompiler/ObjectFile/ObjectFileDB_IR2.cpp
@@ -10,6 +10,7 @@
 #include "common/util/FileUtil.h"
 #include "decompiler/Function/TypeInspector.h"
 #include "decompiler/analysis/reg_usage.h"
+#include "decompiler/analysis/insert_lets.h"
 #include "decompiler/analysis/variable_naming.h"
 #include "decompiler/analysis/cfg_builder.h"
 #include "decompiler/analysis/final_output.h"
@@ -45,6 +46,11 @@ void ObjectFileDB::analyze_functions_ir2(const std::string& output_dir) {
     ir2_store_current_forms();
     lg::info("Expression building...");
     ir2_build_expressions();
+
+    if (get_config().insert_lets) {
+      lg::info("Inserting lets...");
+      ir2_insert_lets();
+    }
   }
 
   if (!output_dir.empty()) {
@@ -422,6 +428,22 @@ void ObjectFileDB::ir2_build_expressions() {
   lg::info("{}/{}/{} expression build in {:.2f} ms\n", successful, attempted, total, timer.getMs());
 }
 
+void ObjectFileDB::ir2_insert_lets() {
+  Timer timer;
+  LetStats combined_stats;
+  int attempted = 0;
+
+  for_each_function_def_order([&](Function& func, int, ObjectFileData&) {
+    if (func.ir2.expressions_succeeded) {
+      attempted++;
+      combined_stats += insert_lets(func, func.ir2.env, *func.ir2.form_pool, func.ir2.top_form);
+    }
+  });
+
+  lg::info("Let pass on {} functions ({}/{} vars in lets) in {:.2f} ms\n", attempted,
+           combined_stats.vars_in_lets, combined_stats.total_vars, timer.getMs());
+}
+
 void ObjectFileDB::ir2_write_results(const std::string& output_dir) {
   Timer timer;
   lg::info("Writing IR2 results to file...");
diff --git a/decompiler/analysis/insert_lets.cpp b/decompiler/analysis/insert_lets.cpp
new file mode 100644
index 000000000..e82e79905
--- /dev/null
+++ b/decompiler/analysis/insert_lets.cpp
@@ -0,0 +1,342 @@
+#include <algorithm>
+
+#include "insert_lets.h"
+
+namespace decompiler {
+
+/*
+Part 1:
+Create a std::unordered_map<ProgVar, std::vector<FormElement*>> which maps a program variable to the
+collection of FormElement* which reference it.
+
+Part 2:
+For each ProgVar, find the lowest common ancestor Form* of the FormElement*'s in the above map.
+
+Part 3:
+For each Form*, find the smallest range of FormElement*s which include all uses of the ProgVar
+
+Part 4:
+Sort these from the largest to smaller range.
+
+This makes sure that at a single level (in the original tree), we insert larger lets first, leaving
+us with only one nesting case to worry about in the next step.
+
+Check the first FormElement* which uses the ProgVar.
+If it is a (set! var xxx), then we can insert a let.
+
+If we are inserting directly inside of another let, at the beginning of that let's body, add to that
+let. This makes the scope larger than it needs to be, but this seems like it will lead to more
+readable code.
+
+If the previous let variables appear in the definition of new one, make the let into a let*
+ */
+
+namespace {
+std::vector<Form*> path_up_tree(Form* in) {
+  std::vector<Form*> path;
+
+  while (in) {
+    path.push_back(in);
+    // lg::warn("In: {}", in->to_string(env));
+    if (in->parent_element) {
+      // lg::warn("  {}", in->parent_element->to_string(env));
+      in = in->parent_element->parent_form;
+    } else {
+      in = nullptr;
+    }
+  }
+  // lg::warn("DONE\n");
+  return path;
+}
+
+Form* lca_form(Form* a, Form* b, const Env& env) {
+  (void)env;
+  if (!a) {
+    return b;
+  }
+
+  // fmt::print("lca {} ({}) and {} ({})\n", a->to_string(env), (void*)a, b->to_string(env),
+  // (void*)b);
+
+  auto a_up = path_up_tree(a);
+  auto b_up = path_up_tree(b);
+
+  int ai = a_up.size() - 1;
+  int bi = b_up.size() - 1;
+
+  Form* result = nullptr;
+  while (ai >= 0 && bi >= 0) {
+    if (a_up.at(ai) == b_up.at(bi)) {
+      result = a_up.at(ai);
+    } else {
+      break;
+    }
+    ai--;
+    bi--;
+  }
+  assert(result);
+
+  // fmt::print("{}\n\n", result->to_string(env));
+  return result;
+}
+}  // namespace
+
+LetStats insert_lets(const Function& func, Env& env, FormPool& pool, Form* top_level_form) {
+  (void)func;
+  //    if (func.guessed_name.to_string() != "(method 4 pair)") {
+  //      return {};
+  //    }
+  LetStats stats;
+
+  // Stored per variable.
+  struct PerVarInfo {
+    std::string var_name;  // name used to uniquely identify
+    RegisterAccess access;
+    std::unordered_set<FormElement*> elts_using_var;  // all FormElements using var
+    Form* lca_form = nullptr;  // the lowest common form that contains all the above elts
+    int start_idx = -1;        // in the above form, first FormElement using var's index
+    int end_idx = -1;          // in the above form, 1 + last FormElement using var's index
+  };
+
+  std::unordered_map<std::string, PerVarInfo> var_info;
+
+  // Part 1, figure out which forms reference each var
+  top_level_form->apply([&](FormElement* elt) {
+    // for each element, figure out what vars we reference:
+    RegAccessSet reg_accesses;
+    elt->collect_vars(reg_accesses, false);
+
+    // and add it.
+    for (auto& access : reg_accesses) {
+      if (access.reg().get_kind() == Reg::FPR || access.reg().get_kind() == Reg::GPR) {
+        auto name = env.get_variable_name(access);
+        var_info[name].elts_using_var.insert(elt);
+        var_info[name].var_name = name;
+        var_info[name].access = access;
+      }
+    }
+  });
+
+  stats.total_vars = var_info.size();
+
+  // Part 2, figure out the lca form which contains all uses of a var
+  for (auto& kv : var_info) {
+    // fmt::print("--------------------- {}\n", kv.first);
+    Form* lca = nullptr;
+    for (auto fe : kv.second.elts_using_var) {
+      lca = lca_form(lca, fe->parent_form, env);
+    }
+    assert(lca);
+    var_info[kv.first].lca_form = lca;
+  }
+
+  // Part 3, find the minimum range of FormElement's within the lca form that contain
+  // all uses. This is the minimum possible range for a set!
+  for (auto& kv : var_info) {
+    // fmt::print("Setting range for let {}\n", kv.first);
+    kv.second.start_idx = std::numeric_limits<int>::max();
+    kv.second.end_idx = std::numeric_limits<int>::min();
+
+    bool got_one = false;
+    for (int i = 0; i < kv.second.lca_form->size(); i++) {
+      RegAccessSet ras;
+      kv.second.lca_form->at(i)->collect_vars(ras, true);
+      bool uses = false;
+      for (auto& ra : ras) {
+        if (env.get_variable_name(ra) == kv.second.var_name) {
+          uses = true;
+        }
+      }
+      if (uses) {
+        //      if (kv.second.elts_using_var.find(kv.second.lca_form->at(i)) !=
+        //          kv.second.elts_using_var.end()) {
+        got_one = true;
+        kv.second.start_idx = std::min(kv.second.start_idx, i);
+        kv.second.end_idx = std::max(kv.second.end_idx, i + 1);
+        // fmt::print("update range {} to {} because of {}\n", kv.second.start_idx,
+        // kv.second.end_idx, kv.second.lca_form->at(i)->to_string(env));
+      }
+    }
+    assert(got_one);
+  }
+
+  // fmt::print("\n");
+
+  // Part 4, sort the var infos in descending size.
+  // this simplifies future passes.
+  std::vector<PerVarInfo> sorted_info;
+  for (auto& kv : var_info) {
+    sorted_info.push_back(kv.second);
+  }
+  std::sort(sorted_info.begin(), sorted_info.end(), [](const PerVarInfo& a, const PerVarInfo& b) {
+    return (a.end_idx - a.start_idx) > (b.end_idx - b.start_idx);
+  });
+
+  // Part 5, find where we want to insert lets.  But don't actually do any insertions.
+  // Only variables that begin with a set! var value can be used in a let, so we may discard
+  // some variables here.  Though I suspect most reasonable functions will not discard any.
+  struct LetInsertion {
+    Form* form = nullptr;
+    int start_elt = -1;  // this is the set!
+    SetVarElement* set_form = nullptr;
+    int end_elt = -1;
+    std::string name;
+  };
+
+  // stored per containing form.
+  std::unordered_map<Form*, std::vector<LetInsertion>> possible_insertions;
+  for (auto& info : sorted_info) {
+    auto first_form = info.lca_form->at(info.start_idx);
+    auto first_form_as_set = dynamic_cast<SetVarElement*>(first_form);
+    if (first_form_as_set &&
+        env.get_variable_name(first_form_as_set->dst()) == env.get_variable_name(info.access) &&
+        !first_form_as_set->info().is_eliminated_coloring_move) {
+      // success!
+      // fmt::print("Want let for {} range {} to {}\n",
+      // env.get_variable_name(first_form_as_set->dst()), info.start_idx, info.end_idx);
+      LetInsertion li;
+      li.form = info.lca_form;
+      li.start_elt = info.start_idx;
+      li.end_elt = info.end_idx;
+      li.set_form = first_form_as_set;
+      li.name = info.var_name;
+      possible_insertions[li.form].push_back(li);
+      stats.vars_in_lets++;
+    } else {
+      // fmt::print("fail for {} : {}\n", info.var_name, first_form->to_string(env));
+    }
+  }
+
+  // Part 6, expand ends of intervals to prevent "tangled lets"
+  for (auto& group : possible_insertions) {
+    // Note : this algorithm is not efficient.
+    bool changed = true;
+    while (changed) {
+      changed = false;
+      for (auto& let_a : group.second) {
+        for (auto& let_b : group.second) {
+          // If b starts within a and ends after a, expand a.
+          if (let_b.start_elt > let_a.start_elt && let_b.start_elt < let_a.end_elt &&
+              let_b.end_elt > let_a.end_elt) {
+            changed = true;
+            // fmt::print("Resized {}'s end to {}\n", let_a.set_form->dst().to_string(env),
+            // let_b.end_elt);
+            let_a.end_elt = let_b.end_elt;
+          }
+        }
+      }
+    }
+  }
+
+  // Part 7: insert lets!
+  for (auto& group : possible_insertions) {
+    // sort decreasing size.
+    std::sort(group.second.begin(), group.second.end(),
+              [](const LetInsertion& a, const LetInsertion& b) {
+                return (a.end_elt - a.start_elt) > (b.end_elt - b.start_elt);
+              });
+
+    // ownership[elt_idx] = the let which actually has this.
+    std::vector<int> ownership;
+    ownership.resize(group.first->size(), -1);
+    for (int let_idx = 0; let_idx < int(group.second.size()); let_idx++) {
+      for (int elt_idx = group.second.at(let_idx).start_elt;
+           elt_idx < group.second.at(let_idx).end_elt; elt_idx++) {
+        ownership.at(elt_idx) = let_idx;
+      }
+    }
+
+    // build lets
+    std::vector<LetElement*> lets;
+    lets.resize(group.first->size(), nullptr);
+    // start at the smallest.
+    for (size_t let_idx = group.second.size(); let_idx-- > 0;) {
+      auto& let_desc = group.second.at(let_idx);
+      std::vector<FormElement*> body;
+      int elt_idx = let_desc.start_elt + 1;  // plus one to skip the variable def.
+      while (elt_idx < let_desc.end_elt) {
+        if (ownership.at(elt_idx) == int(let_idx)) {
+          body.push_back(let_desc.form->at(elt_idx));
+          elt_idx++;
+        } else {
+          auto existing_let = lets.at(ownership[elt_idx]);
+          assert(existing_let);
+          auto& existing_let_info = group.second.at(ownership[elt_idx]);
+          assert(existing_let_info.start_elt == elt_idx);
+          body.push_back(existing_let);
+          elt_idx = existing_let_info.end_elt;
+        }
+      }
+      assert(elt_idx == let_desc.end_elt);
+      auto new_let = pool.alloc_element<LetElement>(pool.alloc_sequence_form(nullptr, body));
+      new_let->add_def(let_desc.set_form->dst(), let_desc.set_form->src());
+      env.set_defined_in_let(let_desc.name);
+      lets.at(let_idx) = new_let;
+    }
+
+    // now rebuild form
+    int elt_idx = 0;
+    std::vector<FormElement*> new_body;
+    while (elt_idx < group.first->size()) {
+      if (ownership.at(elt_idx) == -1) {
+        new_body.push_back(group.first->at(elt_idx));
+        elt_idx++;
+      } else {
+        auto existing_let = lets.at(ownership[elt_idx]);
+        assert(existing_let);
+        auto& existing_let_info = group.second.at(ownership[elt_idx]);
+        assert(existing_let_info.start_elt == elt_idx);
+        new_body.push_back(existing_let);
+        elt_idx = existing_let_info.end_elt;
+      }
+    }
+    assert(elt_idx == group.first->size());
+
+    group.first->elts() = new_body;
+    group.first->claim_all_children();
+  }
+
+  // Part 8: (todo) recognize loops and stuff.
+
+  // Part 9: compact recursive lets:
+  bool changed = true;
+  while (changed) {
+    changed = false;
+    top_level_form->apply([&](FormElement* f) {
+      auto as_let = dynamic_cast<LetElement*>(f);
+      if (!as_let) {
+        return;
+      }
+
+      auto inner_let = dynamic_cast<LetElement*>(as_let->body()->try_as_single_element());
+      if (!inner_let) {
+        return;
+      }
+
+      for (auto& e : inner_let->entries()) {
+        if (!as_let->is_star()) {
+          RegAccessSet used;
+          e.src->collect_vars(used, true);
+          std::unordered_set<std::string> used_by_name;
+          for (auto used_var : used) {
+            used_by_name.insert(env.get_variable_name(used_var));
+          }
+          for (auto& old_entry : as_let->entries()) {
+            if (used_by_name.find(env.get_variable_name(old_entry.dest)) != used_by_name.end()) {
+              as_let->make_let_star();
+              break;
+            }
+          }
+        }
+        as_let->add_entry(e);
+      }
+
+      as_let->set_body(inner_let->body());
+      changed = true;
+    });
+  }
+
+  return stats;
+}
+
+}  // namespace decompiler
\ No newline at end of file
diff --git a/decompiler/analysis/insert_lets.h b/decompiler/analysis/insert_lets.h
new file mode 100644
index 000000000..64e636771
--- /dev/null
+++ b/decompiler/analysis/insert_lets.h
@@ -0,0 +1,21 @@
+#pragma once
+
+#include "decompiler/IR2/Env.h"
+#include "decompiler/Function/Function.h"
+#include "decompiler/IR2/Form.h"
+
+namespace decompiler {
+
+struct LetStats {
+  int total_vars = 0;
+  int vars_in_lets = 0;
+
+  void operator+=(const LetStats& other) {
+    total_vars += other.total_vars;
+    vars_in_lets += other.vars_in_lets;
+  }
+};
+
+LetStats insert_lets(const Function& func, Env& env, FormPool& pool, Form* top_level_form);
+
+}  // namespace decompiler
\ No newline at end of file
diff --git a/decompiler/config.cpp b/decompiler/config.cpp
index 33169920b..2b04e5bd6 100644
--- a/decompiler/config.cpp
+++ b/decompiler/config.cpp
@@ -53,6 +53,7 @@ void set_config(const std::string& path_to_config_file) {
   gConfig.function_type_prop = cfg.at("function_type_prop").get<bool>();
   gConfig.analyze_expressions = cfg.at("analyze_expressions").get<bool>();
   gConfig.run_ir2 = cfg.at("run_ir2").get<bool>();
+  gConfig.insert_lets = cfg.at("insert_lets").get<bool>();
 
   std::vector<std::string> asm_functions_by_name =
       cfg.at("asm_functions_by_name").get<std::vector<std::string>>();
diff --git a/decompiler/config.h b/decompiler/config.h
index d0c63751c..01186ba1d 100644
--- a/decompiler/config.h
+++ b/decompiler/config.h
@@ -40,6 +40,7 @@ struct Config {
   bool write_func_json = false;
   bool function_type_prop = false;
   bool analyze_expressions = false;
+  bool insert_lets = false;
   std::unordered_set<std::string> asm_functions_by_name;
   std::unordered_set<std::string> pair_functions_by_name;
   std::unordered_set<std::string> no_type_analysis_functions_by_name;
diff --git a/decompiler/config/jak1_ntsc_black_label.jsonc b/decompiler/config/jak1_ntsc_black_label.jsonc
index 6d60967c2..efd13c97a 100644
--- a/decompiler/config/jak1_ntsc_black_label.jsonc
+++ b/decompiler/config/jak1_ntsc_black_label.jsonc
@@ -61,6 +61,7 @@
   "analyze_functions":true,
   "analyze_expressions":true,
   "function_type_prop":true,
+  "insert_lets":true,
   "write_disassembly":true,
   "write_hex_near_instructions":false,
 
diff --git a/test/decompiler/FormRegressionTest.cpp b/test/decompiler/FormRegressionTest.cpp
index b71b336e6..99a4130e5 100644
--- a/test/decompiler/FormRegressionTest.cpp
+++ b/test/decompiler/FormRegressionTest.cpp
@@ -5,6 +5,7 @@
 #include "decompiler/analysis/cfg_builder.h"
 #include "decompiler/analysis/expression_build.h"
 #include "decompiler/analysis/final_output.h"
+#include "decompiler/analysis/insert_lets.h"
 #include "common/goos/PrettyPrinter.h"
 #include "decompiler/IR2/Form.h"
 #include "third-party/json.hpp"
@@ -129,7 +130,7 @@ std::unique_ptr<FormRegressionTest::TestData> FormRegressionTest::make_function(
   // for now, just test that this can at least be called.
   if (test->func.ir2.top_form) {
     RegAccessSet vars;
-    test->func.ir2.top_form->collect_vars(vars);
+    test->func.ir2.top_form->collect_vars(vars, true);
 
     if (do_expressions) {
       bool success = convert_to_expressions(test->func.ir2.top_form, *test->func.ir2.form_pool,
@@ -139,6 +140,8 @@ std::unique_ptr<FormRegressionTest::TestData> FormRegressionTest::make_function(
       if (!success) {
         return nullptr;
       }
+      insert_lets(test->func, test->func.ir2.env, *test->func.ir2.form_pool,
+                  test->func.ir2.top_form);
     }
   }
 
diff --git a/test/decompiler/reference/gcommon_REF.gc b/test/decompiler/reference/gcommon_REF.gc
index 3fa637b57..7a29eb6be 100644
--- a/test/decompiler/reference/gcommon_REF.gc
+++ b/test/decompiler/reference/gcommon_REF.gc
@@ -48,9 +48,7 @@
 
 ;; definition for function abs
 (defun abs ((x int))
-  (local-vars (v0-0 int))
-  (set! v0-0 x)
-  (abs v0-0)
+  (let ((v0-0 x)) (abs v0-0))
   )
 
 ;; definition for function min
@@ -118,46 +116,34 @@
    (v0-5 int)
    (v1-0 int)
    (v1-1 int)
-   (a0-1 symbol)
-   (a0-2 symbol)
-   (a0-4 symbol)
-   (a0-5 symbol)
-   (a1-0 string)
-   (a1-1 string)
-   (a1-3 string)
-   (a1-4 string)
    (a2-0 int)
    (a2-1 int)
    (a2-3 int)
-   (t9-0 (function _varargs_ object))
-   (t9-1 (function _varargs_ object))
-   (t9-3 (function _varargs_ object))
-   (t9-4 (function _varargs_ object))
    (gp-0 int)
    )
   (.por gp-0 obj r0-0)
-  (set! t9-0 format)
-  (set! a0-1 #t)
-  (set! a1-0 "[~8x] ~A~%")
-  (.por a2-0 gp-0 r0-0)
-  (t9-0 a0-1 a1-0 a2-0 'vec4s)
-  (set! t9-1 format)
-  (set! a0-2 #t)
-  (set! a1-1 "~Tx: ~f~%")
-  (.sllv a2-1 gp-0 r0-0)
-  (t9-1 a0-2 a1-1 a2-1)
+  (let
+   ((t9-0 format) (a0-1 #t) (a1-0 "[~8x] ~A~%"))
+   (.por a2-0 gp-0 r0-0)
+   (t9-0 a0-1 a1-0 a2-0 'vec4s)
+   )
+  (let
+   ((t9-1 format) (a0-2 #t) (a1-1 "~Tx: ~f~%"))
+   (.sllv a2-1 gp-0 r0-0)
+   (t9-1 a0-2 a1-1 a2-1)
+   )
   (format #t "~Ty: ~f~%" (sar gp-0 32))
-  (set! t9-3 format)
-  (set! a0-4 #t)
-  (set! a1-3 "~Tz: ~f~%")
-  (.pcpyud v1-0 gp-0 r0-0)
-  (.sllv a2-3 v1-0 r0-0)
-  (t9-3 a0-4 a1-3 a2-3)
-  (set! t9-4 format)
-  (set! a0-5 #t)
-  (set! a1-4 "~Tw: ~f~%")
-  (.pcpyud v1-1 gp-0 r0-0)
-  (t9-4 a0-5 a1-4 (sar v1-1 32))
+  (let
+   ((t9-3 format) (a0-4 #t) (a1-3 "~Tz: ~f~%"))
+   (.pcpyud v1-0 gp-0 r0-0)
+   (.sllv a2-3 v1-0 r0-0)
+   (t9-3 a0-4 a1-3 a2-3)
+   )
+  (let
+   ((t9-4 format) (a0-5 #t) (a1-4 "~Tw: ~f~%"))
+   (.pcpyud v1-1 gp-0 r0-0)
+   (t9-4 a0-5 a1-4 (sar v1-1 32))
+   )
   (.por v0-5 gp-0 r0-0)
   (the-as vec4s v0-5)
   )
@@ -170,28 +156,27 @@
    (v0-1 int)
    (v1-0 int)
    (v1-1 int)
-   (a0-1 symbol)
-   (a1-0 string)
    (a2-0 int)
-   (a3-0 int)
    (t0-0 int)
-   (t1-0 int)
    (t2-0 int)
-   (t9-0 (function _varargs_ object))
    (gp-0 int)
    )
   (.por gp-0 obj r0-0)
-  (set! t9-0 format)
-  (set! a0-1 #t)
-  (set! a1-0 "#<vector ~F ~F ~F ~F @ #x~X>")
-  (.sllv a2-0 gp-0 r0-0)
-  (set! a3-0 (sar gp-0 32))
-  (.pcpyud v1-0 gp-0 r0-0)
-  (.sllv t0-0 v1-0 r0-0)
-  (.pcpyud v1-1 gp-0 r0-0)
-  (set! t1-0 (sar v1-1 32))
-  (.por t2-0 gp-0 r0-0)
-  (t9-0 a0-1 a1-0 a2-0 a3-0 t0-0 t1-0 t2-0)
+  (let
+   ((t9-0 format) (a0-1 #t) (a1-0 "#<vector ~F ~F ~F ~F @ #x~X>"))
+   (.sllv a2-0 gp-0 r0-0)
+   (let
+    ((a3-0 (sar gp-0 32)))
+    (.pcpyud v1-0 gp-0 r0-0)
+    (.sllv t0-0 v1-0 r0-0)
+    (.pcpyud v1-1 gp-0 r0-0)
+    (let
+     ((t1-0 (sar v1-1 32)))
+     (.por t2-0 gp-0 r0-0)
+     (t9-0 a0-1 a1-0 a2-0 a3-0 t0-0 t1-0 t2-0)
+     )
+    )
+   )
   (.por v0-1 gp-0 r0-0)
   (the-as vec4s v0-1)
   )
@@ -227,64 +212,70 @@
 
 ;; definition for function basic-type?
 (defun basic-type? ((obj basic) (parent-type type))
-  (local-vars (obj-type type) (end-type type))
-  (set! obj-type (-> obj type))
-  (set! end-type object)
-  (until
-   (begin (set! obj-type (-> obj-type parent)) (= obj-type end-type))
-   (if (= obj-type parent-type) (return #t))
+  (let
+   ((obj-type (-> obj type)) (end-type object))
+   (until
+    (begin (set! obj-type (-> obj-type parent)) (= obj-type end-type))
+    (if (= obj-type parent-type) (return #t))
+    )
    )
   #f
   )
 
 ;; definition for function type-type?
 (defun type-type? ((child-type type) (parent-type type))
-  (local-vars (end-type type))
-  (set! end-type object)
-  (until
-   (begin
-    (set! child-type (-> child-type parent))
-    (or (= child-type end-type) (zero? child-type))
+  (let
+   ((end-type object))
+   (until
+    (begin
+     (set! child-type (-> child-type parent))
+     (or (= child-type end-type) (zero? child-type))
+     )
+    (if (= child-type parent-type) (return #t))
     )
-   (if (= child-type parent-type) (return #t))
    )
   #f
   )
 
 ;; definition for function find-parent-method
 (defun find-parent-method ((child-type type) (method-id int))
-  (local-vars (current-method function) (original-method function))
-  (set! original-method (-> child-type method-table method-id))
-  (until
-   (!= current-method original-method)
-   (if (= child-type object) (return nothing))
-   (set! child-type (-> child-type parent))
-   (set! current-method (-> child-type method-table method-id))
-   (if (zero? current-method) (return nothing))
+  (local-vars (current-method function))
+  (let
+   ((original-method (-> child-type method-table method-id)))
+   (until
+    (!= current-method original-method)
+    (if (= child-type object) (return nothing))
+    (set! child-type (-> child-type parent))
+    (set! current-method (-> child-type method-table method-id))
+    (if (zero? current-method) (return nothing))
+    )
    )
   current-method
   )
 
 ;; definition for function ref
 (defun ref ((lst object) (index int))
-  (local-vars (count int))
-  (set! count 0)
-  (while (< count index) (nop!) (nop!) (set! lst (cdr lst)) (+! count 1))
+  (let
+   ((count 0))
+   (while (< count index) (nop!) (nop!) (set! lst (cdr lst)) (+! count 1))
+   )
   (car lst)
   )
 
 ;; definition for method of type pair
 (defmethod length pair ((obj pair))
-  (local-vars (result int) (iter object))
+  (local-vars (result int))
   (cond
    ((= obj '()) (set! result 0))
    (else
-    (set! iter (cdr obj))
-    (set! result 1)
-    (while
-     (and (!= iter '()) (< (shl (the-as int iter) 62) 0))
-     (+! result 1)
-     (set! iter (cdr iter))
+    (let
+     ((iter (cdr obj)))
+     (set! result 1)
+     (while
+      (and (!= iter '()) (< (shl (the-as int iter) 62) 0))
+      (+! result 1)
+      (set! iter (cdr iter))
+      )
      )
     )
    )
@@ -299,18 +290,20 @@
 
 ;; definition for function last
 (defun last ((lst object))
-  (local-vars (iter object))
-  (set! iter lst)
-  (while (!= (cdr iter) '()) (nop!) (nop!) (set! iter (cdr iter)))
-  iter
+  (let
+   ((iter lst))
+   (while (!= (cdr iter) '()) (nop!) (nop!) (set! iter (cdr iter)))
+   iter
+   )
   )
 
 ;; definition for function member
 (defun member ((obj object) (lst object))
-  (local-vars (iter object))
-  (set! iter lst)
-  (while (not (or (= iter '()) (= (car iter) obj))) (set! iter (cdr iter)))
-  (if (!= iter '()) iter)
+  (let
+   ((iter lst))
+   (while (not (or (= iter '()) (= (car iter) obj))) (set! iter (cdr iter)))
+   (if (!= iter '()) iter)
+   )
   )
 
 ;; definition for function nmember
@@ -324,35 +317,36 @@
 
 ;; definition for function assoc
 (defun assoc ((item object) (alist object))
-  (local-vars (iter object))
-  (set! iter alist)
-  (while
-   (not (or (= iter '()) (= (car (car iter)) item)))
-   (set! iter (cdr iter))
+  (let
+   ((iter alist))
+   (while
+    (not (or (= iter '()) (= (car (car iter)) item)))
+    (set! iter (cdr iter))
+    )
+   (if (!= iter '()) (car iter))
    )
-  (if (!= iter '()) (car iter))
   )
 
 ;; definition for function assoce
 (defun assoce ((item object) (alist object))
-  (local-vars (iter object))
-  (set! iter alist)
-  (while
-   (not (or (= iter '()) (= (car (car iter)) item) (= (car (car iter)) 'else)))
-   (set! iter (cdr iter))
+  (let
+   ((iter alist))
+   (while
+    (not (or (= iter '()) (= (car (car iter)) item) (= (car (car iter)) 'else)))
+    (set! iter (cdr iter))
+    )
+   (if (!= iter '()) (car iter))
    )
-  (if (!= iter '()) (car iter))
   )
 
 ;; definition for function nassoc
 (defun nassoc ((item-name string) (alist object))
-  (local-vars (key object))
   (while
    (not
     (or
      (= alist '())
-     (begin
-      (set! key (car (car alist)))
+     (let
+      ((key (car (car alist))))
       (if
        (pair? key)
        (nmember item-name key)
@@ -368,13 +362,12 @@
 
 ;; definition for function nassoce
 (defun nassoce ((item-name string) (alist object))
-  (local-vars (key object))
   (while
    (not
     (or
      (= alist '())
-     (begin
-      (set! key (car (car alist)))
+     (let
+      ((key (car (car alist))))
       (if
        (pair? key)
        (nmember item-name key)
@@ -390,13 +383,14 @@
 
 ;; definition for function append!
 (defun append! ((front object) (back object))
-  (local-vars (iter object))
   (cond
    ((= front '()) back)
    (else
-    (set! iter front)
-    (while (!= (cdr iter) '()) (nop!) (nop!) (set! iter (cdr iter)))
-    (if (!= iter '()) (set! (cdr iter) back))
+    (let
+     ((iter front))
+     (while (!= (cdr iter) '()) (nop!) (nop!) (set! iter (cdr iter)))
+     (if (!= iter '()) (set! (cdr iter) back))
+     )
     front
     )
    )
@@ -405,20 +399,20 @@
 ;; definition for function delete!
 ;; INFO: Return type mismatch object vs pair.
 (defun delete! ((item object) (lst object))
-  (local-vars (iter-prev object) (iter object))
   (the-as
    pair
    (cond
     ((= item (car lst)) (cdr lst))
     (else
-     (set! iter-prev lst)
-     (set! iter (cdr lst))
-     (while
-      (not (or (= iter '()) (= (car iter) item)))
-      (set! iter-prev iter)
-      (set! iter (cdr iter))
+     (let
+      ((iter-prev lst) (iter (cdr lst)))
+      (while
+       (not (or (= iter '()) (= (car iter) item)))
+       (set! iter-prev iter)
+       (set! iter (cdr iter))
+       )
+      (if (!= iter '()) (set! (cdr iter-prev) (cdr iter)))
       )
-     (if (!= iter '()) (set! (cdr iter-prev) (cdr iter)))
      lst
      )
     )
@@ -427,18 +421,18 @@
 
 ;; definition for function delete-car!
 (defun delete-car! ((item object) (lst object))
-  (local-vars (iter-prev object) (iter object))
   (cond
    ((= item (car (car lst))) (cdr lst))
    (else
-    (set! iter-prev lst)
-    (set! iter (cdr lst))
-    (while
-     (not (or (= iter '()) (= (car (car iter)) item)))
-     (set! iter-prev iter)
-     (set! iter (cdr iter))
+    (let
+     ((iter-prev lst) (iter (cdr lst)))
+     (while
+      (not (or (= iter '()) (= (car (car iter)) item)))
+      (set! iter-prev iter)
+      (set! iter (cdr iter))
+      )
+     (if (!= iter '()) (set! (cdr iter-prev) (cdr iter)))
      )
-    (if (!= iter '()) (set! (cdr iter-prev) (cdr iter)))
     lst
     )
    )
@@ -446,40 +440,38 @@
 
 ;; definition for function insert-cons!
 (defun insert-cons! ((kv object) (alist object))
-  (local-vars (updated-list object))
-  (set! updated-list (delete-car! (car kv) alist))
-  (cons kv updated-list)
+  (let ((updated-list (delete-car! (car kv) alist))) (cons kv updated-list))
   )
 
 ;; definition for function sort
 (defun sort ((lst object) (compare-func (function object object object)))
-  (local-vars
-   (compare-result object)
-   (seoncd-elt object)
-   (first-elt object)
-   (iter object)
-   (unsorted-count int)
-   )
-  (set! unsorted-count -1)
-  (while
-   (nonzero? unsorted-count)
-   (set! unsorted-count 0)
-   (set! iter lst)
+  (let
+   ((unsorted-count -1))
    (while
-    (not (or (= (cdr iter) '()) (>= (shl (the-as int (cdr iter)) 62) 0)))
-    (set! first-elt (car iter))
-    (set! seoncd-elt (car (cdr iter)))
-    (set! compare-result (compare-func first-elt seoncd-elt))
-    (when
-     (and
-      (or (not compare-result) (> (the-as int compare-result) 0))
-      (!= compare-result #t)
+    (nonzero? unsorted-count)
+    (set! unsorted-count 0)
+    (let
+     ((iter lst))
+     (while
+      (not (or (= (cdr iter) '()) (>= (shl (the-as int (cdr iter)) 62) 0)))
+      (let*
+       ((first-elt (car iter))
+        (seoncd-elt (car (cdr iter)))
+        (compare-result (compare-func first-elt seoncd-elt))
+        )
+       (when
+        (and
+         (or (not compare-result) (> (the-as int compare-result) 0))
+         (!= compare-result #t)
+         )
+        (+! unsorted-count 1)
+        (set! (car iter) seoncd-elt)
+        (set! (car (cdr iter)) first-elt)
+        )
+       )
+      (set! iter (cdr iter))
       )
-     (+! unsorted-count 1)
-     (set! (car iter) seoncd-elt)
-     (set! (car (cdr iter)) first-elt)
      )
-    (set! iter (cdr iter))
     )
    )
   lst
@@ -514,27 +506,28 @@
   new
   inline-array-class
   ((allocation symbol) (type-to-make type) (size int))
-  (local-vars (obj inline-array-class))
-  (set!
-   obj
-   (object-new
-    allocation
-    type-to-make
-    (the-as
-     int
-     (+
-      (-> type-to-make size)
-      (* (the-as uint size) (-> type-to-make heap-base))
+  (let
+   ((obj
+     (object-new
+      allocation
+      type-to-make
+      (the-as
+       int
+       (+
+        (-> type-to-make size)
+        (* (the-as uint size) (-> type-to-make heap-base))
+        )
+       )
       )
      )
     )
+   (when
+    (nonzero? obj)
+    (set! (-> obj length) size)
+    (set! (-> obj allocated-length) size)
+    )
+   obj
    )
-  (when
-   (nonzero? obj)
-   (set! (-> obj length) size)
-   (set! (-> obj allocated-length) size)
-   )
-  obj
   )
 
 ;; definition for method of type inline-array-class
@@ -562,37 +555,34 @@
   new
   array
   ((allocation symbol) (type-to-make type) (content-type type) (len int))
-  (local-vars (obj array))
-  (set!
-   obj
-   (object-new
-    allocation
-    type-to-make
-    (the-as
-     int
-     (+
-      (-> type-to-make size)
+  (let
+   ((obj
+     (object-new
+      allocation
+      type-to-make
       (the-as
-       uint
-       (* len (if (type-type? content-type number) (-> content-type size) 4))
+       int
+       (+
+        (-> type-to-make size)
+        (the-as
+         uint
+         (* len (if (type-type? content-type number) (-> content-type size) 4))
+         )
+        )
        )
       )
      )
     )
+   (set! (-> obj allocated-length) len)
+   (set! (-> obj length) len)
+   (set! (-> obj content-type) content-type)
+   obj
    )
-  (set! (-> obj allocated-length) len)
-  (set! (-> obj length) len)
-  (set! (-> obj content-type) content-type)
-  obj
   )
 
 ;; definition for method of type array
 (defmethod print array ((obj array))
   (local-vars
-   (content-type-sym symbol)
-   (v1-42 pointer)
-   (a0-21 symbol)
-   (a1-11 string)
    (a2-8 int)
    (i int)
    (i int)
@@ -606,12 +596,12 @@
    (i int)
    (i int)
    (i int)
-   (t9-10 (function _varargs_ object))
    )
   (format #t "#(")
-  (cond
-   ((type-type? (-> obj content-type) integer)
-    (set! content-type-sym (-> obj content-type symbol))
+  (if
+   (type-type? (-> obj content-type) integer)
+   (let
+    ((content-type-sym (-> obj content-type symbol)))
     (cond
      ((= content-type-sym 'int32)
       (set! i 0)
@@ -687,12 +677,14 @@
         (set! i 0)
         (while
          (< i (-> obj length))
-         (set! t9-10 format)
-         (set! a0-21 #t)
-         (set! a1-11 (if (zero? i) "#x~X" " #x~X"))
-         (set! v1-42 (+ (shl i 4) (the-as int (the-as (array uint128) obj))))
-         (.lq a2-8 12 v1-42)
-         (t9-10 a0-21 a1-11 a2-8)
+         (let
+          ((t9-10 format) (a0-21 #t) (a1-11 (if (zero? i) "#x~X" " #x~X")))
+          (let
+           ((v1-42 (+ (shl i 4) (the-as int (the-as (array uint128) obj)))))
+           (.lq a2-8 12 v1-42)
+           )
+          (t9-10 a0-21 a1-11 a2-8)
+          )
          (+! i 1)
          )
         )
@@ -708,31 +700,29 @@
       )
      )
     )
-   (else
-    (cond
-     ((= (-> obj content-type) float)
-      (set! i 0)
-      (while
-       (< i (-> obj length))
-       (if
-        (zero? i)
-        (format #t "~f" (-> (the-as (array float) obj) i))
-        (format #t " ~f" (-> (the-as (array float) obj) i))
-        )
-       (+! i 1)
+   (cond
+    ((= (-> obj content-type) float)
+     (set! i 0)
+     (while
+      (< i (-> obj length))
+      (if
+       (zero? i)
+       (format #t "~f" (-> (the-as (array float) obj) i))
+       (format #t " ~f" (-> (the-as (array float) obj) i))
        )
+      (+! i 1)
       )
-     (else
-      (set! i 0)
-      (while
-       (< i (-> obj length))
-       (if
-        (zero? i)
-        (format #t "~A" (-> (the-as (array basic) obj) i))
-        (format #t " ~A" (-> (the-as (array basic) obj) i))
-        )
-       (+! i 1)
+     )
+    (else
+     (set! i 0)
+     (while
+      (< i (-> obj length))
+      (if
+       (zero? i)
+       (format #t "~A" (-> (the-as (array basic) obj) i))
+       (format #t " ~A" (-> (the-as (array basic) obj) i))
        )
+      (+! i 1)
       )
      )
     )
@@ -744,11 +734,6 @@
 ;; definition for method of type array
 (defmethod inspect array ((obj array))
   (local-vars
-   (content-type-sym symbol)
-   (v1-42 pointer)
-   (a0-25 symbol)
-   (a1-15 string)
-   (a2-13 int)
    (a3-10 int)
    (i int)
    (i int)
@@ -762,16 +747,16 @@
    (i int)
    (i int)
    (i int)
-   (t9-14 (function _varargs_ object))
    )
   (format #t "[~8x] ~A~%" obj (-> obj type))
   (format #t "~Tallocated-length: ~D~%" (-> obj allocated-length))
   (format #t "~Tlength: ~D~%" (-> obj length))
   (format #t "~Tcontent-type: ~A~%" (-> obj content-type))
   (format #t "~Tdata[~D]: @ #x~X~%" (-> obj allocated-length) (-> obj data))
-  (cond
-   ((type-type? (-> obj content-type) integer)
-    (set! content-type-sym (-> obj content-type symbol))
+  (if
+   (type-type? (-> obj content-type) integer)
+   (let
+    ((content-type-sym (-> obj content-type symbol)))
     (cond
      ((= content-type-sym 'int32)
       (set! i 0)
@@ -843,13 +828,11 @@
         (set! i 0)
         (while
          (< i (-> obj length))
-         (set! t9-14 format)
-         (set! a0-25 #t)
-         (set! a1-15 "~T  [~D] #x~X~%")
-         (set! a2-13 i)
-         (set! v1-42 (+ (shl i 4) (the-as int obj)))
-         (.lq a3-10 12 v1-42)
-         (t9-14 a0-25 a1-15 a2-13 a3-10)
+         (let
+          ((t9-14 format) (a0-25 #t) (a1-15 "~T  [~D] #x~X~%") (a2-13 i))
+          (let ((v1-42 (+ (shl i 4) (the-as int obj)))) (.lq a3-10 12 v1-42))
+          (t9-14 a0-25 a1-15 a2-13 a3-10)
+          )
          (+! i 1)
          )
         )
@@ -865,23 +848,21 @@
       )
      )
     )
-   (else
-    (cond
-     ((= (-> obj content-type) float)
-      (set! i 0)
-      (while
-       (< i (-> obj length))
-       (format #t "~T  [~D] ~f~%" i (-> obj i))
-       (+! i 1)
-       )
+   (cond
+    ((= (-> obj content-type) float)
+     (set! i 0)
+     (while
+      (< i (-> obj length))
+      (format #t "~T  [~D] ~f~%" i (-> obj i))
+      (+! i 1)
       )
-     (else
-      (set! i 0)
-      (while
-       (< i (-> obj length))
-       (format #t "~T  [~D] ~A~%" i (-> obj i))
-       (+! i 1)
-       )
+     )
+    (else
+     (set! i 0)
+     (while
+      (< i (-> obj length))
+      (format #t "~T  [~D] ~A~%" i (-> obj i))
+      (+! i 1)
       )
      )
     )
@@ -918,90 +899,104 @@
 
 ;; definition for function mem-copy!
 (defun mem-copy! ((dst pointer) (src pointer) (size int))
-  (local-vars (result pointer) (i int))
-  (set! result dst)
-  (set! i 0)
-  (while
-   (< i size)
-   (set! (-> (the-as (pointer int8) dst)) (-> (the-as (pointer uint8) src)))
-   (&+! dst 1)
-   (&+! src 1)
-   (+! i 1)
+  (let
+   ((result dst))
+   (let
+    ((i 0))
+    (while
+     (< i size)
+     (set! (-> (the-as (pointer int8) dst)) (-> (the-as (pointer uint8) src)))
+     (&+! dst 1)
+     (&+! src 1)
+     (+! i 1)
+     )
+    )
+   result
    )
-  result
   )
 
 ;; definition for function qmem-copy<-!
 (defun qmem-copy<-! ((dst pointer) (src pointer) (size int))
-  (local-vars (result pointer) (qwc int) (value int))
-  (set! result dst)
-  (set! qwc (sar (+ size 15) 4))
-  (while
-   (nonzero? qwc)
-   (+! qwc -1)
-   (.lq value 0 src)
-   (.sq value 0 dst)
-   (&+! dst 16)
-   (&+! src 16)
+  (local-vars (value int))
+  (let
+   ((result dst))
+   (let
+    ((qwc (sar (+ size 15) 4)))
+    (while
+     (nonzero? qwc)
+     (+! qwc -1)
+     (.lq value 0 src)
+     (.sq value 0 dst)
+     (&+! dst 16)
+     (&+! src 16)
+     )
+    )
+   result
    )
-  result
   )
 
 ;; definition for function qmem-copy->!
 (defun qmem-copy->! ((dst pointer) (src pointer) (size int))
-  (local-vars
-   (result pointer)
-   (qwc int)
-   (src-ptr pointer)
-   (dst-ptr pointer)
-   (value int)
+  (local-vars (src-ptr pointer) (dst-ptr pointer) (value int))
+  (let
+   ((result dst))
+   (let
+    ((qwc (sar (+ size 15) 4)))
+    (&+! dst (shl qwc 4))
+    (&+! src (shl qwc 4))
+    (while
+     (nonzero? qwc)
+     (+! qwc -1)
+     (&+! src-ptr -16)
+     (&+! dst-ptr -16)
+     (.lq value 0 dst-ptr)
+     (.sq value 0 src-ptr)
+     )
+    )
+   result
    )
-  (set! result dst)
-  (set! qwc (sar (+ size 15) 4))
-  (&+! dst (shl qwc 4))
-  (&+! src (shl qwc 4))
-  (while
-   (nonzero? qwc)
-   (+! qwc -1)
-   (&+! src-ptr -16)
-   (&+! dst-ptr -16)
-   (.lq value 0 dst-ptr)
-   (.sq value 0 src-ptr)
-   )
-  result
   )
 
 ;; definition for function mem-set32!
 (defun mem-set32! ((dst pointer) (size int) (value int))
-  (local-vars (result pointer) (i int))
-  (set! result dst)
-  (set! i 0)
-  (while
-   (< i size)
-   (set! (-> (the-as (pointer int32) dst)) value)
-   (&+! dst 4)
-   (nop!)
-   (+! i 1)
+  (let
+   ((result dst))
+   (let
+    ((i 0))
+    (while
+     (< i size)
+     (set! (-> (the-as (pointer int32) dst)) value)
+     (&+! dst 4)
+     (nop!)
+     (+! i 1)
+     )
+    )
+   result
    )
-  result
   )
 
 ;; definition for function mem-or!
 (defun mem-or! ((dst pointer) (src pointer) (size int))
-  (local-vars (result pointer) (i int))
-  (set! result dst)
-  (set! i 0)
-  (while
-   (< i size)
-   (set!
-    (-> (the-as (pointer int8) dst))
-    (logior (-> (the-as (pointer uint8) dst)) (-> (the-as (pointer uint8) src)))
+  (let
+   ((result dst))
+   (let
+    ((i 0))
+    (while
+     (< i size)
+     (set!
+      (-> (the-as (pointer int8) dst))
+      (logior
+       (-> (the-as (pointer uint8) dst))
+       (-> (the-as (pointer uint8) src))
+       )
+      )
+     (&+! dst 1)
+     (&+! src 1)
+     (+! i 1)
+     )
     )
-   (&+! dst 1)
-   (&+! src 1)
-   (+! i 1)
+   result
    )
-  result
   )
 
 ;; definition for function quad-copy!
@@ -1022,9 +1017,7 @@
 
 ;; definition for function printl
 (defun printl ((arg0 object))
-  (local-vars (a0-1 object))
-  (set! a0-1 arg0)
-  ((method-of-type (rtype-of a0-1) print) a0-1)
+  (let ((a0-1 arg0)) ((method-of-type (rtype-of a0-1) print) a0-1))
   (format #t "~%")
   arg0
   )
@@ -1036,20 +1029,21 @@
 
 ;; definition (debug) for function mem-print
 (defun-debug mem-print ((data (pointer uint32)) (word-count int))
-  (local-vars (current-qword int))
-  (set! current-qword 0)
-  (while
-   (< current-qword (sar word-count 2))
-   (format
-    0
-    "~X: ~X ~X ~X ~X~%"
-    (&-> data (shl current-qword 2))
-    (-> data (shl current-qword 2))
-    (-> data (+ (shl current-qword 2) 1))
-    (-> data (+ (shl current-qword 2) 2))
-    (-> data (+ (shl current-qword 2) 3))
+  (let
+   ((current-qword 0))
+   (while
+    (< current-qword (sar word-count 2))
+    (format
+     0
+     "~X: ~X ~X ~X ~X~%"
+     (&-> data (shl current-qword 2))
+     (-> data (shl current-qword 2))
+     (-> data (+ (shl current-qword 2) 1))
+     (-> data (+ (shl current-qword 2) 2))
+     (-> data (+ (shl current-qword 2) 3))
+     )
+    (+! current-qword 1)
     )
-   (+! current-qword 1)
    )
   #f
   )
@@ -1059,13 +1053,14 @@
 
 ;; definition for function print-tree-bitmask
 (defun print-tree-bitmask ((bits int) (count int))
-  (local-vars (i int))
-  (set! i 0)
-  (while
-   (< i count)
-   (if (zero? (logand bits 1)) (format #t "    ") (format #t "|   "))
-   (set! bits (shr bits 1))
-   (+! i 1)
+  (let
+   ((i 0))
+   (while
+    (< i count)
+    (if (zero? (logand bits 1)) (format #t "    ") (format #t "|   "))
+    (set! bits (shr bits 1))
+    (+! i 1)
+    )
    )
   #f
   )
@@ -1087,251 +1082,244 @@
    (allow-false basic)
    (print-dest object)
    )
-  (local-vars
-   (in-goal-mem symbol)
-   (v1-10 int)
-   (v1-11 int)
-   (v1-43 int)
-   (v1-44 int)
-   (v1-47 int)
-   (v1-48 int)
-   (s7-0 none)
-   )
-  (set!
-   in-goal-mem
-   (and
-    (>= (the-as uint obj) (the-as uint __START-OF-TABLE__))
-    (< (the-as uint obj) (the-as uint #x8000000))
-    )
-   )
-  (cond
-   ((not expected-type)
-    (cond
-     ((nonzero? (logand (the-as int obj) 3))
-      (if
-       name
-       (format
-        print-dest
-        "ERROR: object #x~X ~S is not a valid object (misaligned)~%"
-        obj
-        name
-        )
-       )
-      #f
+  (local-vars (v1-11 int) (v1-44 int) (v1-48 int) (s7-0 none))
+  (let
+   ((in-goal-mem
+     (and
+      (>= (the-as uint obj) (the-as uint __START-OF-TABLE__))
+      (< (the-as uint obj) (the-as uint #x8000000))
       )
-     ((not in-goal-mem)
-      (if
-       name
-       (format
-        print-dest
-        "ERROR: object #x~X ~S is not a valid object (bad address)~%"
-        obj
-        name
-        )
-       )
-      #f
-      )
-     (else #t)
      )
     )
-   ((and allow-false (not obj)) #t)
-   (else
-    (cond
-     ((= expected-type structure)
-      (cond
-       ((nonzero? (logand (the-as int obj) 15))
-        (if
-         name
-         (format
-          print-dest
-          "ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%"
-          obj
-          name
-          expected-type
-          )
-         )
-        #f
-        )
-       ((or
-         (not in-goal-mem)
-         (begin
-          (set! v1-10 #x8000)
-          (.daddu v1-11 v1-10 s7-0)
-          (< (the-as uint obj) (the-as uint v1-11))
-          )
-         )
-        (if
-         name
-         (format
-          print-dest
-          "ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%"
-          obj
-          name
-          expected-type
-          )
-         )
-        #f
-        )
-       (else #t)
-       )
-      )
-     ((= expected-type pair)
-      (cond
-       ((!= (logand (the-as int obj) 7) 2)
-        (if
-         name
-         (format
-          print-dest
-          "ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%"
-          obj
-          name
-          expected-type
-          )
-         )
-        #f
-        )
-       ((not in-goal-mem)
-        (if
-         name
-         (format
-          print-dest
-          "ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%"
-          obj
-          name
-          expected-type
-          )
-         )
-        #f
-        )
-       (else #t)
-       )
-      )
-     ((= expected-type binteger)
-      (cond
-       ((zero? (logand (the-as int obj) 7)) #t)
-       (else
-        (if
-         name
-         (format
-          print-dest
-          "ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%"
-          obj
-          name
-          expected-type
-          )
-         )
-        #f
-        )
-       )
-      )
-     ((!= (logand (the-as int obj) 7) 4)
-      (if
-       name
-       (format
-        print-dest
-        "ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%"
-        obj
+   (cond
+    ((not expected-type)
+     (cond
+      ((nonzero? (logand (the-as int obj) 3))
+       (if
         name
-        expected-type
-        )
-       )
-      #f
-      )
-     ((not in-goal-mem)
-      (if
-       name
-       (format
-        print-dest
-        "ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%"
-        obj
-        name
-        expected-type
-        )
-       )
-      #f
-      )
-     ((and (= expected-type type) (!= (rtype-of obj) type))
-      (if
-       name
-       (format
-        print-dest
-        "ERROR: object #x~X ~S is not a valid object of type '~A' (invalid type #x~X)~%"
-        obj
-        name
-        expected-type
-        (rtype-of obj)
-        )
-       )
-      #f
-      )
-     (else
-      (cond
-       ((and (!= expected-type type) (not (valid? (rtype-of obj) type #f #t 0)))
-        (if
+        (format
+         print-dest
+         "ERROR: object #x~X ~S is not a valid object (misaligned)~%"
+         obj
          name
-         (format
-          print-dest
-          "ERROR: object #x~X ~S is not a valid object of type '~A' (invalid type #x~X)~%"
-          obj
-          name
-          expected-type
-          (rtype-of obj)
-          )
          )
-        #f
         )
-       ((not (type-type? (rtype-of obj) expected-type))
-        (if
+       #f
+       )
+      ((not in-goal-mem)
+       (if
+        name
+        (format
+         print-dest
+         "ERROR: object #x~X ~S is not a valid object (bad address)~%"
+         obj
          name
-         (format
-          print-dest
-          "ERROR: object #x~X ~S is not a valid object of type '~A' (is type '~A' instead)~%"
-          obj
-          name
-          expected-type
-          (rtype-of obj)
-          )
          )
-        #f
         )
-       ((= expected-type symbol)
-        (set! v1-43 #x8000)
-        (.daddu v1-44 v1-43 s7-0)
-        (cond
-         ((>= (the-as uint obj) (the-as uint v1-44))
-          (if
+       #f
+       )
+      (else #t)
+      )
+     )
+    ((and allow-false (not obj)) #t)
+    (else
+     (cond
+      ((= expected-type structure)
+       (cond
+        ((nonzero? (logand (the-as int obj) 15))
+         (if
+          name
+          (format
+           print-dest
+           "ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%"
+           obj
            name
-           (format
-            print-dest
-            "ERROR: object #x~X ~S is not a valid object of type '~A' (not in symbol table)~%"
-            obj
-            name
-            expected-type
-            )
+           expected-type
            )
-          #f
           )
-         (else #t)
+         #f
          )
-        )
-       ((begin
-         (set! v1-47 #x8000)
-         (.daddu v1-48 v1-47 s7-0)
-         (< (the-as uint obj) (the-as uint v1-48))
-         )
-        (if
-         name
-         (format
-          print-dest
-          "ERROR: object #x~X ~S is not a valid object of type '~A' (inside symbol table)~%"
-          obj
+        ((or
+          (not in-goal-mem)
+          (begin
+           (let ((v1-10 #x8000)) (.daddu v1-11 v1-10 s7-0))
+           (< (the-as uint obj) (the-as uint v1-11))
+           )
+          )
+         (if
           name
-          expected-type
+          (format
+           print-dest
+           "ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%"
+           obj
+           name
+           expected-type
+           )
+          )
+         #f
+         )
+        (else #t)
+        )
+       )
+      ((= expected-type pair)
+       (cond
+        ((!= (logand (the-as int obj) 7) 2)
+         (if
+          name
+          (format
+           print-dest
+           "ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%"
+           obj
+           name
+           expected-type
+           )
+          )
+         #f
+         )
+        ((not in-goal-mem)
+         (if
+          name
+          (format
+           print-dest
+           "ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%"
+           obj
+           name
+           expected-type
+           )
+          )
+         #f
+         )
+        (else #t)
+        )
+       )
+      ((= expected-type binteger)
+       (cond
+        ((zero? (logand (the-as int obj) 7)) #t)
+        (else
+         (if
+          name
+          (format
+           print-dest
+           "ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%"
+           obj
+           name
+           expected-type
+           )
+          )
+         #f
+         )
+        )
+       )
+      ((!= (logand (the-as int obj) 7) 4)
+       (if
+        name
+        (format
+         print-dest
+         "ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%"
+         obj
+         name
+         expected-type
+         )
+        )
+       #f
+       )
+      ((not in-goal-mem)
+       (if
+        name
+        (format
+         print-dest
+         "ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%"
+         obj
+         name
+         expected-type
+         )
+        )
+       #f
+       )
+      ((and (= expected-type type) (!= (rtype-of obj) type))
+       (if
+        name
+        (format
+         print-dest
+         "ERROR: object #x~X ~S is not a valid object of type '~A' (invalid type #x~X)~%"
+         obj
+         name
+         expected-type
+         (rtype-of obj)
+         )
+        )
+       #f
+       )
+      (else
+       (cond
+        ((and
+          (!= expected-type type)
+          (not (valid? (rtype-of obj) type #f #t 0))
+          )
+         (if
+          name
+          (format
+           print-dest
+           "ERROR: object #x~X ~S is not a valid object of type '~A' (invalid type #x~X)~%"
+           obj
+           name
+           expected-type
+           (rtype-of obj)
+           )
+          )
+         #f
+         )
+        ((not (type-type? (rtype-of obj) expected-type))
+         (if
+          name
+          (format
+           print-dest
+           "ERROR: object #x~X ~S is not a valid object of type '~A' (is type '~A' instead)~%"
+           obj
+           name
+           expected-type
+           (rtype-of obj)
+           )
+          )
+         #f
+         )
+        ((= expected-type symbol)
+         (let ((v1-43 #x8000)) (.daddu v1-44 v1-43 s7-0))
+         (cond
+          ((>= (the-as uint obj) (the-as uint v1-44))
+           (if
+            name
+            (format
+             print-dest
+             "ERROR: object #x~X ~S is not a valid object of type '~A' (not in symbol table)~%"
+             obj
+             name
+             expected-type
+             )
+            )
+           #f
+           )
+          (else #t)
           )
          )
-        #f
+        ((begin
+          (let ((v1-47 #x8000)) (.daddu v1-48 v1-47 s7-0))
+          (< (the-as uint obj) (the-as uint v1-48))
+          )
+         (if
+          name
+          (format
+           print-dest
+           "ERROR: object #x~X ~S is not a valid object of type '~A' (inside symbol table)~%"
+           obj
+           name
+           expected-type
+           )
+          )
+         #f
+         )
+        (else #t)
         )
-       (else #t)
        )
       )
      )
@@ -1340,5 +1328,4 @@
   )
 
 ;; failed to figure out what this is:
-(set! v0-3 0)
-
+(let ((v0-3 0)))
diff --git a/test/decompiler/test_FormExpressionBuild.cpp b/test/decompiler/test_FormExpressionBuild.cpp
index aa33cfcb6..4a0da8109 100644
--- a/test/decompiler/test_FormExpressionBuild.cpp
+++ b/test/decompiler/test_FormExpressionBuild.cpp
@@ -266,7 +266,7 @@ TEST_F(FormRegressionTest, ExprAbs) {
       "    jr ra\n"
       "    daddu sp, sp, r0";
   std::string type = "(function int int)";
-  std::string expected = "(begin (set! v0-0 arg0) (abs v0-0))";
+  std::string expected = "(let ((v0-0 arg0)) (abs v0-0))";
   test_with_expr(func, type, expected);
 }
 
@@ -454,14 +454,11 @@ TEST_F(FormRegressionTest, ExprBasicTypeP) {
   std::string type = "(function basic type symbol)";
   std::string expected =
       "(begin\n"
-      "  (set! v1-0 (-> arg0 type))\n"
-      "  (set! a0-1 object)\n"
-      "  (until\n"
-      "   (begin (set! v1-0 (-> v1-0 parent)) (= v1-0 a0-1))\n"  // likely using set! as value. we
-                                                                 // don't plan on supporting this.
-      "   (if\n"
-      "    (= v1-0 arg1)\n"
-      "    (return #t)\n"
+      "  (let\n"
+      "   ((v1-0 (-> arg0 type)) (a0-1 object))\n"
+      "   (until\n"
+      "    (begin (set! v1-0 (-> v1-0 parent)) (= v1-0 a0-1))\n"
+      "    (if (= v1-0 arg1) (return #t))\n"
       "    )\n"
       "   )\n"
       "  #f\n"
@@ -497,17 +494,14 @@ TEST_F(FormRegressionTest, FinalBasicTypeP) {
   std::string type = "(function basic type symbol)";
   std::string expected =
       "(defun test-function ((arg0 basic) (arg1 type))\n"
-      "  (local-vars\n"
-      "   (v1-0 type)\n"
-      "   (a0-1 type)\n"
-      "   )\n"
-      "   (set! v1-0 (-> arg0 type))\n"
-      "   (set! a0-1 object)\n"
+      "  (let\n"
+      "   ((v1-0 (-> arg0 type)) (a0-1 object))\n"
       "   (until\n"
       "    (begin (set! v1-0 (-> v1-0 parent)) (= v1-0 a0-1))\n"
       "    (if (= v1-0 arg1) (return #t))\n"
       "    )\n"
-      "   #f\n"
+      "   )\n"
+      "  #f\n"
       "  )";
   test_final_function(func, type, expected);
 }
@@ -553,13 +547,12 @@ TEST_F(FormRegressionTest, ExprTypeTypep) {
 
   std::string expected =
       "(begin\n"
-      "  (set! v1-0 object)\n"
-      "  (until\n"
-      "   (begin\n"
-      "    (set! arg0 (-> arg0 parent))\n"
-      "    (or (= arg0 v1-0) (zero? arg0))\n"
+      "  (let\n"
+      "   ((v1-0 object))\n"
+      "   (until\n"
+      "    (begin (set! arg0 (-> arg0 parent)) (or (= arg0 v1-0) (zero? arg0)))\n"
+      "    (if (= arg0 arg1) (return #t))\n"
       "    )\n"
-      "   (if (= arg0 arg1) (return #t))\n"
       "   )\n"
       "  #f\n"
       "  )";
@@ -615,13 +608,15 @@ TEST_F(FormRegressionTest, ExprFindParentMethod) {
 
   std::string expected =
       "(begin\n"
-      "  (set! v1-2 (-> arg0 method-table arg1))\n"
-      "  (until\n"
-      "   (!= v0-0 v1-2)\n"
-      "   (if (= arg0 object) (return nothing))\n"
-      "   (set! arg0 (-> arg0 parent))\n"
-      "   (set! v0-0 (-> arg0 method-table arg1))\n"
-      "   (if (zero? v0-0) (return nothing))\n"
+      "  (let\n"
+      "   ((v1-2 (-> arg0 method-table arg1)))\n"
+      "   (until\n"
+      "    (!= v0-0 v1-2)\n"
+      "    (if (= arg0 object) (return nothing))\n"
+      "    (set! arg0 (-> arg0 parent))\n"
+      "    (set! v0-0 (-> arg0 method-table arg1))\n"
+      "    (if (zero? v0-0) (return nothing))\n"
+      "    )\n"
       "   )\n"
       "  v0-0\n"
       "  )";
@@ -656,13 +651,9 @@ TEST_F(FormRegressionTest, ExprRef) {
 
   std::string expected =
       "(begin\n"
-      "  (set! v1-0 0)\n"
-      "  (while\n"
-      "   (< v1-0 arg1)\n"
-      "   (nop!)\n"
-      "   (nop!)\n"
-      "   (set! arg0 (cdr arg0))\n"
-      "   (+! v1-0 1)\n"
+      "  (let\n"
+      "   ((v1-0 0))\n"
+      "   (while (< v1-0 arg1) (nop!) (nop!) (set! arg0 (cdr arg0)) (+! v1-0 1))\n"
       "   )\n"
       "  (car arg0)\n"
       "  )";
@@ -715,19 +706,20 @@ TEST_F(FormRegressionTest, ExprPairMethod4) {
       "    daddu sp, sp, r0\n";
   std::string type = "(function pair int)";
 
+  // multiple return paths merged variable issue.
   std::string expected =
       "(begin\n"
       "  (cond\n"
-      "   ((= arg0 '()) (set! v0-0 0))\n"
+      "   ((= arg0 (quote ())) (set! v0-0 0))\n"
       "   (else\n"
-      "    (set! v1-1 (cdr arg0))\n"
-      "    (set! v0-0 1)\n"
-      "    (while\n"
-      "      (and (!= v1-1 '()) "
-      "                   (< (shl (the-as int v1-1) 62) 0)\n"
+      "    (let\n"
+      "     ((v1-1 (cdr arg0)))\n"
+      "     (set! v0-0 1)\n"
+      "     (while\n"
+      "      (and (!= v1-1 (quote ())) (< (shl (the-as int v1-1) 62) 0))\n"
+      "      (+! v0-0 1)\n"
+      "      (set! v1-1 (cdr v1-1))\n"
       "      )\n"
-      "     (+! v0-0 1)\n"
-      "     (set! v1-1 (cdr v1-1))\n"
       "     )\n"
       "    )\n"
       "   )\n"
@@ -774,12 +766,9 @@ TEST_F(FormRegressionTest, ExprLast) {
   std::string type = "(function object object)";
 
   std::string expected =
-      "(begin\n"
-      "  (set! v0-0 arg0)\n"
-      "  (while (!= (cdr v0-0) '())"
-      "     (nop!)\n"
-      "     (nop!)\n"
-      "     (set! v0-0 (cdr v0-0)))\n"
+      "(let\n"
+      "  ((v0-0 arg0))\n"
+      "  (while (!= (cdr v0-0) (quote ())) (nop!) (nop!) (set! v0-0 (cdr v0-0)))\n"
       "  v0-0\n"
       "  )";
   test_with_expr(func, type, expected, true, "");
@@ -826,13 +815,13 @@ TEST_F(FormRegressionTest, ExprMember) {
   std::string type = "(function object object object)";
 
   std::string expected =
-      "(begin\n"
-      "  (set! v1-0 arg1)\n"
+      "(let\n"
+      "  ((v1-0 arg1))\n"
       "  (while\n"
-      "   (not (or (= v1-0 '()) (= (car v1-0) arg0)))\n"
+      "   (not (or (= v1-0 (quote ())) (= (car v1-0) arg0)))\n"
       "   (set! v1-0 (cdr v1-0))\n"
       "   )\n"
-      "  (if (!= v1-0 '()) v1-0)\n"
+      "  (if (!= v1-0 (quote ())) v1-0)\n"
       "  )";
   test_with_expr(func, type, expected, true, "");
 }
@@ -939,13 +928,13 @@ TEST_F(FormRegressionTest, ExprAssoc) {
   std::string type = "(function object object object)";
 
   std::string expected =
-      "(begin\n"
-      "  (set! v1-0 arg1)\n"
+      "(let\n"
+      "  ((v1-0 arg1))\n"
       "  (while\n"
-      "   (not (or (= v1-0 '()) (= (car (car v1-0)) arg0)))\n"
+      "   (not (or (= v1-0 (quote ())) (= (car (car v1-0)) arg0)))\n"
       "   (set! v1-0 (cdr v1-0))\n"
       "   )\n"
-      "  (if (!= v1-0 '()) (car v1-0))\n"
+      "  (if (!= v1-0 (quote ())) (car v1-0))\n"
       "  )";
   test_with_expr(func, type, expected, true, "");
 }
@@ -1001,19 +990,19 @@ TEST_F(FormRegressionTest, ExprAssoce) {
   std::string type = "(function object object object)";
 
   std::string expected =
-      "(begin\n"
-      "  (set! v1-0 arg1)\n"
+      "(let\n"
+      "  ((v1-0 arg1))\n"
       "  (while\n"
       "   (not\n"
       "    (or\n"
-      "     (= v1-0 '())\n"
+      "     (= v1-0 (quote ()))\n"
       "     (= (car (car v1-0)) arg0)\n"
-      "     (= (car (car v1-0)) 'else)\n"
+      "     (= (car (car v1-0)) (quote else))\n"
       "     )\n"
       "    )\n"
       "   (set! v1-0 (cdr v1-0))\n"
       "   )\n"
-      "  (if (!= v1-0 '()) (car v1-0))\n"
+      "  (if (!= v1-0 (quote ())) (car v1-0))\n"
       "  )";
   test_with_expr(func, type, expected, true, "");
 }
@@ -1092,13 +1081,13 @@ TEST_F(FormRegressionTest, ExprNassoc) {
       "   (not\n"
       "    (or\n"
       "     (= arg1 (quote ()))\n"
-      "     (begin\n"
-      "      (set! a1-1 (car (car arg1)))\n"
-      "      (if "
+      "     (let\n"
+      "      ((a1-1 (car (car arg1))))\n"
+      "      (if\n"
       "       (pair? a1-1)\n"
       "       (nmember (the-as basic arg0) a1-1)\n"
-      "       (name= (the-as basic a1-1) (the-as basic arg0))"
-      "      )\n"
+      "       (name= (the-as basic a1-1) (the-as basic arg0))\n"
+      "       )\n"
       "      )\n"
       "     )\n"
       "    )\n"
@@ -1194,8 +1183,8 @@ TEST_F(FormRegressionTest, ExprNassoce) {
       "   (not\n"
       "    (or\n"
       "     (= arg1 (quote ()))\n"
-      "     (begin\n"
-      "      (set! s4-0 (car (car arg1)))\n"
+      "     (let\n"
+      "      ((s4-0 (car (car arg1))))\n"
       "      (if\n"
       "       (pair? s4-0)\n"
       "       (nmember (the-as basic arg0) s4-0)\n"
@@ -1260,11 +1249,13 @@ TEST_F(FormRegressionTest, ExprAppend) {
 
   std::string expected =
       "(cond\n"
-      "  ((= arg0 '()) arg1)\n"
+      "  ((= arg0 (quote ())) arg1)\n"
       "  (else\n"
-      "   (set! v1-1 arg0)\n"
-      "   (while (!= (cdr v1-1) '()) (nop!) (nop!) (set! v1-1 (cdr v1-1)))\n"
-      "   (if (!= v1-1 '()) (set! (cdr v1-1) arg1))\n"
+      "   (let\n"
+      "    ((v1-1 arg0))\n"
+      "    (while (!= (cdr v1-1) (quote ())) (nop!) (nop!) (set! v1-1 (cdr v1-1)))\n"
+      "    (if (!= v1-1 (quote ())) (set! (cdr v1-1) arg1))\n"
+      "    )\n"
       "   arg0\n"
       "   )\n"
       "  )";
@@ -1332,14 +1323,15 @@ TEST_F(FormRegressionTest, ExprDelete) {
       "  (cond\n"
       "   ((= arg0 (car arg1)) (cdr arg1))\n"
       "   (else\n"
-      "    (set! v1-1 arg1)\n"
-      "    (set! a2-0 (cdr arg1))\n"
-      "    (while\n"
-      "     (not (or (= a2-0 (quote ())) (= (car a2-0) arg0)))\n"
-      "     (set! v1-1 a2-0)\n"
-      "     (set! a2-0 (cdr a2-0))\n"
+      "    (let\n"
+      "     ((v1-1 arg1) (a2-0 (cdr arg1)))\n"
+      "     (while\n"
+      "      (not (or (= a2-0 (quote ())) (= (car a2-0) arg0)))\n"
+      "      (set! v1-1 a2-0)\n"
+      "      (set! a2-0 (cdr a2-0))\n"
+      "      )\n"
+      "     (if (!= a2-0 (quote ())) (set! (cdr v1-1) (cdr a2-0)))\n"
       "     )\n"
-      "    (if (!= a2-0 (quote ())) (set! (cdr v1-1) (cdr a2-0)))\n"
       "    arg1\n"
       "    )\n"
       "   )\n"
@@ -1410,14 +1402,15 @@ TEST_F(FormRegressionTest, ExprDeleteCar) {
       "  (cond\n"
       "   ((= arg0 (car (car arg1))) (cdr arg1))\n"
       "   (else\n"
-      "    (set! v1-2 arg1)\n"
-      "    (set! a2-0 (cdr arg1))\n"
-      "    (while\n"
-      "     (not (or (= a2-0 (quote ())) (= (car (car a2-0)) arg0)))\n"
-      "     (set! v1-2 a2-0)\n"
-      "     (set! a2-0 (cdr a2-0))\n"
+      "    (let\n"
+      "     ((v1-2 arg1) (a2-0 (cdr arg1)))\n"
+      "     (while\n"
+      "      (not (or (= a2-0 (quote ())) (= (car (car a2-0)) arg0)))\n"
+      "      (set! v1-2 a2-0)\n"
+      "      (set! a2-0 (cdr a2-0))\n"
+      "      )\n"
+      "     (if (!= a2-0 (quote ())) (set! (cdr v1-2) (cdr a2-0)))\n"
       "     )\n"
-      "    (if (!= a2-0 (quote ())) (set! (cdr v1-2) (cdr a2-0)))\n"
       "    arg1\n"
       "    )\n"
       "   )\n"
@@ -1454,11 +1447,7 @@ TEST_F(FormRegressionTest, ExprInsertCons) {
   std::string type = "(function object object pair)";
 
   // NOTE - this appears to _not_ be a nested call.
-  std::string expected =
-      "(begin\n"
-      "  (set! a3-0 (delete-car! (car arg0) arg1))\n"
-      "  (cons arg0 a3-0)\n"
-      "  )";
+  std::string expected = "(let ((a3-0 (delete-car! (car arg0) arg1))) (cons arg0 a3-0))";
   test_with_expr(func, type, expected, true, "");
 }
 
@@ -1568,25 +1557,29 @@ TEST_F(FormRegressionTest, ExprSort) {
   // TODO - this should probably be tested.
   std::string expected =
       "(begin\n"
-      "  (set! s4-0 -1)\n"
-      "  (while\n"
-      "   (nonzero? s4-0)\n"
-      "   (set! s4-0 0)\n"
-      "   (set! s3-0 arg0)\n"
+      "  (let\n"
+      "   ((s4-0 -1))\n"
       "   (while\n"
-      "    (not\n"
-      "     (or (= (cdr s3-0) (quote ())) (>= (shl (the-as int (cdr s3-0)) 62) 0))\n"
+      "    (nonzero? s4-0)\n"
+      "    (set! s4-0 0)\n"
+      "    (let\n"
+      "     ((s3-0 arg0))\n"
+      "     (while\n"
+      "      (not\n"
+      "       (or (= (cdr s3-0) (quote ())) (>= (shl (the-as int (cdr s3-0)) 62) 0))\n"
+      "       )\n"
+      "      (let*\n"
+      "       ((s2-0 (car s3-0)) (s1-0 (car (cdr s3-0))) (v1-1 (arg1 s2-0 s1-0)))\n"
+      "       (when\n"
+      "        (and (or (not v1-1) (> (the-as int v1-1) 0)) (!= v1-1 #t))\n"
+      "        (+! s4-0 1)\n"
+      "        (set! (car s3-0) s1-0)\n"
+      "        (set! (car (cdr s3-0)) s2-0)\n"
+      "        )\n"
+      "       )\n"
+      "      (set! s3-0 (cdr s3-0))\n"
+      "      )\n"
       "     )\n"
-      "    (set! s2-0 (car s3-0))\n"
-      "    (set! s1-0 (car (cdr s3-0)))\n"
-      "    (set! v1-1 (arg1 s2-0 s1-0))\n"
-      "    (when\n"
-      "     (and (or (not v1-1) (> (the-as int v1-1) 0)) (!= v1-1 #t))\n"
-      "     (+! s4-0 1)\n"
-      "     (set! (car s3-0) s1-0)\n"
-      "     (set! (car (cdr s3-0)) s2-0)\n"
-      "     )\n"
-      "    (set! s3-0 (cdr s3-0))\n"
       "    )\n"
       "   )\n"
       "  arg0\n"
@@ -1627,13 +1620,13 @@ TEST_F(FormRegressionTest, ExprInlineArrayMethod0) {
   std::string type = "(function symbol type int inline-array-class)";
 
   std::string expected =
-      "(begin\n"
-      "  (set!\n"
-      "   v0-0\n"
-      "   (object-new\n"
-      "    arg0\n"
-      "    arg1\n"
-      "    (the-as int (+ (-> arg1 size) (* (the-as uint arg2) (-> arg1 heap-base))))\n"
+      "(let\n"
+      "  ((v0-0\n"
+      "    (object-new\n"
+      "     arg0\n"
+      "     arg1\n"
+      "     (the-as int (+ (-> arg1 size) (* (the-as uint arg2) (-> arg1 heap-base))))\n"
+      "     )\n"
       "    )\n"
       "   )\n"
       "  (when\n"
@@ -1743,17 +1736,17 @@ TEST_F(FormRegressionTest, ExprArrayMethod0) {
   std::string type = "(function symbol type type int array)";
 
   std::string expected =
-      "(begin\n"
-      "  (set!\n"
-      "   v0-1\n"
-      "   (object-new\n"
-      "    arg0\n"
-      "    arg1\n"
-      "    (the-as\n"
-      "     int\n"
-      "     (+\n"
-      "      (-> arg1 size)\n"
-      "      (the-as uint (* arg3 (if (type-type? arg2 number) (-> arg2 size) 4)))\n"
+      "(let\n"
+      "  ((v0-1\n"
+      "    (object-new\n"
+      "     arg0\n"
+      "     arg1\n"
+      "     (the-as\n"
+      "      int\n"
+      "      (+\n"
+      "       (-> arg1 size)\n"
+      "       (the-as uint (* arg3 (if (type-type? arg2 number) (-> arg2 size) 4)))\n"
+      "       )\n"
       "      )\n"
       "     )\n"
       "    )\n"
@@ -1867,15 +1860,17 @@ TEST_F(FormRegressionTest, ExprMemCopy) {
   std::string type = "(function pointer pointer int pointer)";
 
   std::string expected =
-      "(begin\n"
-      "  (set! v0-0 arg0)\n"
-      "  (set! v1-0 0)\n"
-      "  (while\n"
-      "   (< v1-0 arg2)\n"
-      "   (set! (-> (the-as (pointer int8) arg0)) (-> (the-as (pointer uint8) arg1)))\n"
-      "   (&+! arg0 1)\n"
-      "   (&+! arg1 1)\n"
-      "   (+! v1-0 1)\n"
+      "(let\n"
+      "  ((v0-0 arg0))\n"
+      "  (let\n"
+      "   ((v1-0 0))\n"
+      "   (while\n"
+      "    (< v1-0 arg2)\n"
+      "    (set! (-> (the-as (pointer int8) arg0)) (-> (the-as (pointer uint8) arg1)))\n"
+      "    (&+! arg0 1)\n"
+      "    (&+! arg1 1)\n"
+      "    (+! v1-0 1)\n"
+      "    )\n"
       "   )\n"
       "  v0-0\n"
       "  )";
@@ -1908,15 +1903,17 @@ TEST_F(FormRegressionTest, ExprMemSet32) {
   std::string type = "(function pointer int int pointer)";
 
   std::string expected =
-      "(begin\n"
-      "  (set! v0-0 arg0)\n"
-      "  (set! v1-0 0)\n"
-      "  (while\n"
-      "   (< v1-0 arg1)\n"
-      "   (set! (-> (the-as (pointer int32) arg0)) arg2)\n"
-      "   (&+! arg0 4)\n"
-      "   (nop!)\n"
-      "   (+! v1-0 1)\n"
+      "(let\n"
+      "  ((v0-0 arg0))\n"
+      "  (let\n"
+      "   ((v1-0 0))\n"
+      "   (while\n"
+      "    (< v1-0 arg1)\n"
+      "    (set! (-> (the-as (pointer int32) arg0)) arg2)\n"
+      "    (&+! arg0 4)\n"
+      "    (nop!)\n"
+      "    (+! v1-0 1)\n"
+      "    )\n"
       "   )\n"
       "  v0-0\n"
       "  )";
@@ -1952,21 +1949,23 @@ TEST_F(FormRegressionTest, ExprMemOr) {
   std::string type = "(function pointer pointer int pointer)";
 
   std::string expected =
-      "(begin\n"
-      "  (set! v0-0 arg0)\n"
-      "  (set! v1-0 0)\n"
-      "  (while\n"
-      "   (< v1-0 arg2)\n"
-      "   (set!\n"
-      "    (-> (the-as (pointer int8) arg0))\n"
-      "    (logior\n"
-      "     (-> (the-as (pointer uint8) arg0))\n"
-      "     (-> (the-as (pointer uint8) arg1))\n"
+      "(let\n"
+      "  ((v0-0 arg0))\n"
+      "  (let\n"
+      "   ((v1-0 0))\n"
+      "   (while\n"
+      "    (< v1-0 arg2)\n"
+      "    (set!\n"
+      "     (-> (the-as (pointer int8) arg0))\n"
+      "     (logior\n"
+      "      (-> (the-as (pointer uint8) arg0))\n"
+      "      (-> (the-as (pointer uint8) arg1))\n"
+      "      )\n"
       "     )\n"
+      "    (&+! arg0 1)\n"
+      "    (&+! arg1 1)\n"
+      "    (+! v1-0 1)\n"
       "    )\n"
-      "   (&+! arg0 1)\n"
-      "   (&+! arg1 1)\n"
-      "   (+! v1-0 1)\n"
       "   )\n"
       "  v0-0\n"
       "  )";
@@ -2076,8 +2075,7 @@ TEST_F(FormRegressionTest, ExprPrintl) {
 
   std::string expected =
       "(begin\n"
-      "  (set! a0-1 arg0)\n"
-      "  ((method-of-type (rtype-of a0-1) print) a0-1)\n"
+      "  (let ((a0-1 arg0)) ((method-of-type (rtype-of a0-1) print) a0-1))\n"
       "  (format #t \"~%\")\n"
       "  arg0\n"
       "  )";
@@ -2173,16 +2171,14 @@ TEST_F(FormRegressionTest, ExprPrintTreeBitmask) {
 
   std::string expected =
       "(begin\n"
-      "  (set! s4-0 0)\n"
-      "  (while\n"
-      "   (< s4-0 arg1)\n"
-      "   (if\n"
-      "    (zero? (logand arg0 1))\n"
-      "    (format #t \"    \")\n"
-      "    (format #t \"|   \")\n"
+      "  (let\n"
+      "   ((s4-0 0))\n"
+      "   (while\n"
+      "    (< s4-0 arg1)\n"
+      "    (if (zero? (logand arg0 1)) (format #t \"    \") (format #t \"|   \"))\n"
+      "    (set! arg0 (shr arg0 1))\n"
+      "    (+! s4-0 1)\n"
       "    )\n"
-      "   (set! arg0 (shr arg0 1))\n"
-      "   (+! s4-0 1)\n"
       "   )\n"
       "  #f\n"
       "  )";
@@ -2351,7 +2347,7 @@ TEST_F(FormRegressionTest, ExprStopwatchElapsedSeconds) {
       "    daddiu sp, sp, 16";
   std::string type = "(function int float)";
 
-  std::string expected = "(begin (set! v1-0 (abs arg0)) (* (l.f L20) (the float v1-0)))";
+  std::string expected = "(let ((v1-0 (abs arg0))) (* (l.f L20) (the float v1-0)))";
   test_with_expr(func, type, expected, false, "");
 }
 
@@ -2381,17 +2377,23 @@ TEST_F(FormRegressionTest, ExprCopyStringString) {
       "    jr ra\n"
       "    daddu sp, sp, r0";
   std::string type = "(function string string string)";
+  // this is correct, but an example of where let's might look better if nested,
+  // even if it means making the scope a little bit larger...
   std::string expected =
       "(begin\n"
-      "  (set! v1-0 (-> arg0 data))\n"
-      "  (set! a1-1 (-> arg1 data))\n"
-      "  (while\n"
-      "   (nonzero? (-> a1-1 0))\n"
-      "   (set! (-> v1-0 0) (-> a1-1 0))\n"
-      "   (set! v1-0 (&-> v1-0 1))\n"
-      "   (set! a1-1 (&-> a1-1 1))\n"
+      "  (let\n"
+      "   ((v1-0 (-> arg0 data)))\n"
+      "   (let\n"
+      "    ((a1-1 (-> arg1 data)))\n"
+      "    (while\n"
+      "     (nonzero? (-> a1-1 0))\n"
+      "     (set! (-> v1-0 0) (-> a1-1 0))\n"
+      "     (set! v1-0 (&-> v1-0 1))\n"
+      "     (set! a1-1 (&-> a1-1 1))\n"
+      "     )\n"
+      "    )\n"
+      "   (set! (-> v1-0 0) 0)\n"
       "   )\n"
-      "  (set! (-> v1-0 0) 0)\n"
       "  arg0\n"
       "  )";
   test_with_expr(func, type, expected, false, "");
@@ -2485,21 +2487,23 @@ TEST_F(FormRegressionTest, StringLt) {
   std::string type = "(function string string symbol)";
   std::string expected =
       "(begin\n"
-      "  (set!\n"
-      "   s4-1\n"
-      "   (min\n"
-      "    ((method-of-type string length) arg0)\n"
-      "    ((method-of-type string length) arg1)\n"
+      "  (let\n"
+      "   ((s4-1\n"
+      "     (min\n"
+      "      ((method-of-type string length) arg0)\n"
+      "      ((method-of-type string length) arg1)\n"
+      "      )\n"
+      "     )\n"
+      "    (v1-4 0)\n"
       "    )\n"
-      "   )\n"
-      "  (set! v1-4 0)\n"
-      "  (while\n"
-      "   (< v1-4 s4-1)\n"
-      "   (cond\n"
-      "    ((< (-> arg0 data v1-4) (-> arg1 data v1-4)) (return #t))\n"
-      "    ((< (-> arg1 data v1-4) (-> arg0 data v1-4)) (return #f))\n"
+      "   (while\n"
+      "    (< v1-4 s4-1)\n"
+      "    (cond\n"
+      "     ((< (-> arg0 data v1-4) (-> arg1 data v1-4)) (return #t))\n"
+      "     ((< (-> arg1 data v1-4) (-> arg0 data v1-4)) (return #f))\n"
+      "     )\n"
+      "    (+! v1-4 1)\n"
       "    )\n"
-      "   (+! v1-4 1)\n"
       "   )\n"
       "  #f\n"
       "  )";
@@ -2567,8 +2571,8 @@ TEST_F(FormRegressionTest, ExprTerminal2) {
   std::string type = "(function float float float float float)";
 
   std::string expected =
-      "(begin\n"
-      "  (set! f0-4 (sqrt (/ (- (* 0.000000 arg0) arg1) arg2)))\n"
+      "(let\n"
+      "  ((f0-4 (sqrt (/ (- (* 0.0 arg0) arg1) arg2))))\n"
       "  (- f0-4 (+ arg1 (* arg2 (* f0-4 f0-4))))\n"
       "  )";
   test_with_expr(func, type, expected, false, "", {{"L17", "A ~A"}});
diff --git a/test/decompiler/test_FormExpressionBuildLong.cpp b/test/decompiler/test_FormExpressionBuildLong.cpp
index b248c821d..2be3e3c4a 100644
--- a/test/decompiler/test_FormExpressionBuildLong.cpp
+++ b/test/decompiler/test_FormExpressionBuildLong.cpp
@@ -539,144 +539,165 @@ TEST_F(FormRegressionTest, ExprArrayMethod2) {
   std::string expected =
       "(begin\n"
       "  (format #t \"#(\")\n"
-      "  (cond\n"
-      "   ((type-type? (-> arg0 content-type) integer)\n"
-      "    (set! v1-1 (-> arg0 content-type symbol))\n"
+      "  (if\n"
+      "   (type-type? (-> arg0 content-type) integer)\n"
+      "   (let\n"
+      "    ((v1-1 (-> arg0 content-type symbol)))\n"
       "    (cond\n"
       "     ((= v1-1 (quote int32))\n"
-      "      (set! s5-0 0)\n"
-      "      (while\n"
-      "       (< s5-0 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        (if (zero? s5-0) \"~D\" \" ~D\")\n"
-      "        (-> (the-as (array int32) arg0) s5-0)\n"
+      "      (let\n"
+      "       ((s5-0 0))\n"
+      "       (while\n"
+      "        (< s5-0 (-> arg0 length))\n"
+      "        (format\n"
+      "         #t\n"
+      "         (if (zero? s5-0) \"~D\" \" ~D\")\n"
+      "         (-> (the-as (array int32) arg0) s5-0)\n"
+      "         )\n"
+      "        (+! s5-0 1)\n"
       "        )\n"
-      "       (+! s5-0 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote uint32))\n"
-      "      (set! s5-1 0)\n"
-      "      (while\n"
-      "       (< s5-1 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        (if (zero? s5-1) \"~D\" \" ~D\")\n"
-      "        (-> (the-as (array uint32) arg0) s5-1)\n"
+      "      (let\n"
+      "       ((s5-1 0))\n"
+      "       (while\n"
+      "        (< s5-1 (-> arg0 length))\n"
+      "        (format\n"
+      "         #t\n"
+      "         (if (zero? s5-1) \"~D\" \" ~D\")\n"
+      "         (-> (the-as (array uint32) arg0) s5-1)\n"
+      "         )\n"
+      "        (+! s5-1 1)\n"
       "        )\n"
-      "       (+! s5-1 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote int64))\n"
-      "      (set! s5-2 0)\n"
-      "      (while\n"
-      "       (< s5-2 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        (if (zero? s5-2) \"~D\" \" ~D\")\n"
-      "        (-> (the-as (array int64) arg0) s5-2)\n"
+      "      (let\n"
+      "       ((s5-2 0))\n"
+      "       (while\n"
+      "        (< s5-2 (-> arg0 length))\n"
+      "        (format\n"
+      "         #t\n"
+      "         (if (zero? s5-2) \"~D\" \" ~D\")\n"
+      "         (-> (the-as (array int64) arg0) s5-2)\n"
+      "         )\n"
+      "        (+! s5-2 1)\n"
       "        )\n"
-      "       (+! s5-2 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote uint64))\n"
-      "      (set! s5-3 0)\n"
-      "      (while\n"
-      "       (< s5-3 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        (if (zero? s5-3) \"#x~X\" \" #x~X\")\n"
-      "        (-> (the-as (array uint64) arg0) s5-3)\n"
+      "      (let\n"
+      "       ((s5-3 0))\n"
+      "       (while\n"
+      "        (< s5-3 (-> arg0 length))\n"
+      "        (format\n"
+      "         #t\n"
+      "         (if (zero? s5-3) \"#x~X\" \" #x~X\")\n"
+      "         (-> (the-as (array uint64) arg0) s5-3)\n"
+      "         )\n"
+      "        (+! s5-3 1)\n"
       "        )\n"
-      "       (+! s5-3 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote int8))\n"
-      "      (set! s5-4 0)\n"
-      "      (while\n"
-      "       (< s5-4 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        (if (zero? s5-4) \"~D\" \" ~D\")\n"
-      "        (-> (the-as (array int8) arg0) s5-4)\n"
+      "      (let\n"
+      "       ((s5-4 0))\n"
+      "       (while\n"
+      "        (< s5-4 (-> arg0 length))\n"
+      "        (format\n"
+      "         #t\n"
+      "         (if (zero? s5-4) \"~D\" \" ~D\")\n"
+      "         (-> (the-as (array int8) arg0) s5-4)\n"
+      "         )\n"
+      "        (+! s5-4 1)\n"
       "        )\n"
-      "       (+! s5-4 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote uint8))\n"
-      "      (set! s5-5 0)\n"
-      "      (while\n"
-      "       (< s5-5 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        (if (zero? s5-5) \"~D\" \" ~D\")\n"
-      "        (-> (the-as (array uint8) arg0) s5-5)\n"
+      "      (let\n"
+      "       ((s5-5 0))\n"
+      "       (while\n"
+      "        (< s5-5 (-> arg0 length))\n"
+      "        (format\n"
+      "         #t\n"
+      "         (if (zero? s5-5) \"~D\" \" ~D\")\n"
+      "         (-> (the-as (array uint8) arg0) s5-5)\n"
+      "         )\n"
+      "        (+! s5-5 1)\n"
       "        )\n"
-      "       (+! s5-5 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote int16))\n"
-      "      (set! s5-6 0)\n"
-      "      (while\n"
-      "       (< s5-6 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        (if (zero? s5-6) \"~D\" \" ~D\")\n"
-      "        (-> (the-as (array int16) arg0) s5-6)\n"
+      "      (let\n"
+      "       ((s5-6 0))\n"
+      "       (while\n"
+      "        (< s5-6 (-> arg0 length))\n"
+      "        (format\n"
+      "         #t\n"
+      "         (if (zero? s5-6) \"~D\" \" ~D\")\n"
+      "         (-> (the-as (array int16) arg0) s5-6)\n"
+      "         )\n"
+      "        (+! s5-6 1)\n"
       "        )\n"
-      "       (+! s5-6 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote uint16))\n"
-      "      (set! s5-7 0)\n"
-      "      (while\n"
-      "       (< s5-7 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        (if (zero? s5-7) \"~D\" \" ~D\")\n"
-      "        (-> (the-as (array uint16) arg0) s5-7)\n"
+      "      (let\n"
+      "       ((s5-7 0))\n"
+      "       (while\n"
+      "        (< s5-7 (-> arg0 length))\n"
+      "        (format\n"
+      "         #t\n"
+      "         (if (zero? s5-7) \"~D\" \" ~D\")\n"
+      "         (-> (the-as (array uint16) arg0) s5-7)\n"
+      "         )\n"
+      "        (+! s5-7 1)\n"
       "        )\n"
-      "       (+! s5-7 1)\n"
       "       )\n"
       "      )\n"
       "     (else\n"
       "      (cond\n"
       "       ((or (= v1-1 (quote uint128)) (= v1-1 (quote int128)))\n"
-      "        (set! s5-8 0)\n"
-      "        (while\n"
-      "         (< s5-8 (-> arg0 length))\n"
-      "         (set! t9-10 format)\n"
-      "         (set! a0-21 #t)\n"
-      "         (set! a1-11 (if (zero? s5-8) \"#x~X\" \" #x~X\"))\n"
-      "         (set!\n"
-      "          v1-42\n"
-      "          (+ (shl s5-8 4) (the-as int (the-as (array uint128) arg0)))\n"
+      "        (let\n"
+      "         ((s5-8 0))\n"
+      "         (while\n"
+      "          (< s5-8 (-> arg0 length))\n"
+      "          (let\n"
+      "           ((t9-10 format) (a0-21 #t) (a1-11 (if (zero? s5-8) \"#x~X\" \" #x~X\")))\n"
+      "           (let\n"
+      "            ((v1-42 (+ (shl s5-8 4) (the-as int (the-as (array uint128) arg0))))\n"
+      "             )\n"
+      "            (.lq a2-8 12 v1-42)\n"
+      "            )\n"
+      "           (t9-10 a0-21 a1-11 a2-8)\n"
+      "           )\n"
+      "          (+! s5-8 1)\n"
       "          )\n"
-      "         (.lq a2-8 12 v1-42)\n"
-      "         (t9-10 a0-21 a1-11 a2-8)\n"
-      "         (+! s5-8 1)\n"
       "         )\n"
       "        )\n"
       "       (else\n"
-      "        (set! s5-9 0)\n"
-      "        (while\n"
-      "         (< s5-9 (-> arg0 length))\n"
-      "         (format\n"
-      "          #t\n"
-      "          (if (zero? s5-9) \"~D\" \" ~D\")\n"
-      "          (-> (the-as (array int32) arg0) s5-9)\n"
+      "        (let\n"
+      "         ((s5-9 0))\n"
+      "         (while\n"
+      "          (< s5-9 (-> arg0 length))\n"
+      "          (format\n"
+      "           #t\n"
+      "           (if (zero? s5-9) \"~D\" \" ~D\")\n"
+      "           (-> (the-as (array int32) arg0) s5-9)\n"
+      "           )\n"
+      "          (+! s5-9 1)\n"
       "          )\n"
-      "         (+! s5-9 1)\n"
       "         )\n"
       "        )\n"
       "       )\n"
       "      )\n"
       "     )\n"
       "    )\n"
-      "   (else\n"
-      "    (cond\n"
-      "     ((= (-> arg0 content-type) float)\n"
-      "      (set! s5-10 0)\n"
+      "   (cond\n"
+      "    ((= (-> arg0 content-type) float)\n"
+      "     (let\n"
+      "      ((s5-10 0))\n"
       "      (while\n"
       "       (< s5-10 (-> arg0 length))\n"
       "       (if\n"
@@ -687,8 +708,10 @@ TEST_F(FormRegressionTest, ExprArrayMethod2) {
       "       (+! s5-10 1)\n"
       "       )\n"
       "      )\n"
-      "     (else\n"
-      "      (set! s5-11 0)\n"
+      "     )\n"
+      "    (else\n"
+      "     (let\n"
+      "      ((s5-11 0))\n"
       "      (while\n"
       "       (< s5-11 (-> arg0 length))\n"
       "       (if\n"
@@ -1192,176 +1215,148 @@ TEST_F(FormRegressionTest, ExprArrayMethod3) {
       "  (format #t \"~Tallocated-length: ~D~%\" (-> arg0 allocated-length))\n"
       "  (format #t \"~Tlength: ~D~%\" (-> arg0 length))\n"
       "  (format #t \" ~Tcontent-type: ~A~%\" (-> arg0 content-type))\n"
-      "  (format\n"
-      "   #t\n"
-      "   \"~Tdata[~D]: @ #x~X~%\"\n"
-      "   (-> arg0 allocated-length)\n"
-      "   (-> arg0 data)\n"
-      "   )\n"
-      "  (cond\n"
-      "   ((type-type? (-> arg0 content-type) integer)\n"
-      "    (set! v1-1 (-> arg0 content-type symbol))\n"
+      "  (format #t \"~Tdata[~D]: @ #x~X~%\" (-> arg0 allocated-length) (-> arg0 data))\n"
+      "  (if\n"
+      "   (type-type? (-> arg0 content-type) integer)\n"
+      "   (let\n"
+      "    ((v1-1 (-> arg0 content-type symbol)))\n"
       "    (cond\n"
       "     ((= v1-1 (quote int32))\n"
-      "      (set! s5-0 0)\n"
-      "      (while\n"
-      "       (< s5-0 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] ~D~%\"\n"
-      "        s5-0\n"
-      "        (-> (the-as (array int32) arg0) s5-0)\n"
+      "      (let\n"
+      "       ((s5-0 0))\n"
+      "       (while\n"
+      "        (< s5-0 (-> arg0 length))\n"
+      "        (format #t \"~T  [~D] ~D~%\" s5-0 (-> (the-as (array int32) arg0) s5-0))\n"
+      "        (+! s5-0 1)\n"
       "        )\n"
-      "       (+! s5-0 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote uint32))\n"
-      "      (set! s5-1 0)\n"
-      "      (while\n"
-      "       (< s5-1 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] ~D~%\"\n"
-      "        s5-1\n"
-      "        (-> (the-as (array uint32) arg0) s5-1)\n"
+      "      (let\n"
+      "       ((s5-1 0))\n"
+      "       (while\n"
+      "        (< s5-1 (-> arg0 length))\n"
+      "        (format #t \"~T  [~D] ~D~%\" s5-1 (-> (the-as (array uint32) arg0) s5-1))\n"
+      "        (+! s5-1 1)\n"
       "        )\n"
-      "       (+! s5-1 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote int64))\n"
-      "      (set! s5-2 0)\n"
-      "      (while\n"
-      "       (< s5-2 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] ~D~%\"\n"
-      "        s5-2\n"
-      "        (-> (the-as (array int64) arg0) s5-2)\n"
+      "      (let\n"
+      "       ((s5-2 0))\n"
+      "       (while\n"
+      "        (< s5-2 (-> arg0 length))\n"
+      "        (format #t \"~T  [~D] ~D~%\" s5-2 (-> (the-as (array int64) arg0) s5-2))\n"
+      "        (+! s5-2 1)\n"
       "        )\n"
-      "       (+! s5-2 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote uint64))\n"
-      "      (set! s5-3 0)\n"
-      "      (while\n"
-      "       (< s5-3 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] #x~X~%\"\n"
-      "        s5-3\n"
-      "        (-> (the-as (array uint64) arg0) s5-3)\n"
+      "      (let\n"
+      "       ((s5-3 0))\n"
+      "       (while\n"
+      "        (< s5-3 (-> arg0 length))\n"
+      "        (format\n"
+      "         #t\n"
+      "         \"~T  [~D] #x~X~%\"\n"
+      "         s5-3\n"
+      "         (-> (the-as (array uint64) arg0) s5-3)\n"
+      "         )\n"
+      "        (+! s5-3 1)\n"
       "        )\n"
-      "       (+! s5-3 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote int8))\n"
-      "      (set! s5-4 0)\n"
-      "      (while\n"
-      "       (< s5-4 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] ~D~%\"\n"
-      "        s5-4\n"
-      "        (-> (the-as (array int8) arg0) s5-4)\n"
+      "      (let\n"
+      "       ((s5-4 0))\n"
+      "       (while\n"
+      "        (< s5-4 (-> arg0 length))\n"
+      "        (format #t \"~T  [~D] ~D~%\" s5-4 (-> (the-as (array int8) arg0) s5-4))\n"
+      "        (+! s5-4 1)\n"
       "        )\n"
-      "       (+! s5-4 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote uint8))\n"
-      "      (set! s5-5 0)\n"
-      "      (while\n"
-      "       (< s5-5 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] ~D~%\"\n"
-      "        s5-5\n"
-      "        (-> (the-as (array int8) arg0) s5-5)\n"
+      "      (let\n"
+      "       ((s5-5 0))\n"
+      "       (while\n"
+      "        (< s5-5 (-> arg0 length))\n"
+      "        (format #t \"~T  [~D] ~D~%\" s5-5 (-> (the-as (array int8) arg0) s5-5))\n"
+      "        (+! s5-5 1)\n"
       "        )\n"
-      "       (+! s5-5 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote int16))\n"
-      "      (set! s5-6 0)\n"
-      "      (while\n"
-      "       (< s5-6 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] ~D~%\"\n"
-      "        s5-6\n"
-      "        (-> (the-as (array int16) arg0) s5-6)\n"
+      "      (let\n"
+      "       ((s5-6 0))\n"
+      "       (while\n"
+      "        (< s5-6 (-> arg0 length))\n"
+      "        (format #t \"~T  [~D] ~D~%\" s5-6 (-> (the-as (array int16) arg0) s5-6))\n"
+      "        (+! s5-6 1)\n"
       "        )\n"
-      "       (+! s5-6 1)\n"
       "       )\n"
       "      )\n"
       "     ((= v1-1 (quote uint16))\n"
-      "      (set! s5-7 0)\n"
-      "      (while\n"
-      "       (< s5-7 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] ~D~%\"\n"
-      "        s5-7\n"
-      "        (-> (the-as (array uint16) arg0) s5-7)\n"
+      "      (let\n"
+      "       ((s5-7 0))\n"
+      "       (while\n"
+      "        (< s5-7 (-> arg0 length))\n"
+      "        (format #t \"~T  [~D] ~D~%\" s5-7 (-> (the-as (array uint16) arg0) s5-7))\n"
+      "        (+! s5-7 1)\n"
       "        )\n"
-      "       (+! s5-7 1)\n"
       "       )\n"
       "      )\n"
       "     (else\n"
       "      (cond\n"
       "       ((or (= v1-1 (quote int128)) (= v1-1 (quote uint128)))\n"
-      "        (set! s5-8 0)\n"
-      "        (while\n"
-      "         (< s5-8 (-> arg0 length))\n"
-      "         (set! t9-14 format)\n"
-      "         (set! a0-25 #t)\n"
-      "         (set! a1-15 \"~T  [~D] #x~X~%\")\n"
-      "         (set! a2-13 s5-8)\n"
-      "         (set!\n"
-      "          v1-42\n"
-      "          (+ (shl s5-8 4) (the-as int (the-as (array uint128) arg0)))\n"
+      "        (let\n"
+      "         ((s5-8 0))\n"
+      "         (while\n"
+      "          (< s5-8 (-> arg0 length))\n"
+      "          (let\n"
+      "           ((t9-14 format) (a0-25 #t) (a1-15 \"~T  [~D] #x~X~%\") (a2-13 s5-8))\n"
+      "           (let\n"
+      "            ((v1-42 (+ (shl s5-8 4) (the-as int (the-as (array uint128) arg0))))\n"
+      "             )\n"
+      "            (.lq a3-10 12 v1-42)\n"
+      "            )\n"
+      "           (t9-14 a0-25 a1-15 a2-13 a3-10)\n"
+      "           )\n"
+      "          (+! s5-8 1)\n"
       "          )\n"
-      "         (.lq a3-10 12 v1-42)\n"
-      "         (t9-14 a0-25 a1-15 a2-13 a3-10)\n"
-      "         (+! s5-8 1)\n"
       "         )\n"
       "        )\n"
       "       (else\n"
-      "        (set! s5-9 0)\n"
-      "        (while\n"
-      "         (< s5-9 (-> arg0 length))\n"
-      "         (format #t \"~T  [~D] ~D~%\" s5-9 (-> arg0 s5-9))\n"
-      "         (+! s5-9 1)\n"
+      "        (let\n"
+      "         ((s5-9 0))\n"
+      "         (while\n"
+      "          (< s5-9 (-> arg0 length))\n"
+      "          (format #t \"~T  [~D] ~D~%\" s5-9 (-> arg0 s5-9))\n"
+      "          (+! s5-9 1)\n"
+      "          )\n"
       "         )\n"
       "        )\n"
       "       )\n"
       "      )\n"
       "     )\n"
       "    )\n"
-      "   (else\n"
-      "    (cond\n"
-      "     ((= (-> arg0 content-type) float)\n"
-      "      (set! s5-10 0)\n"
+      "   (cond\n"
+      "    ((= (-> arg0 content-type) float)\n"
+      "     (let\n"
+      "      ((s5-10 0))\n"
       "      (while\n"
       "       (< s5-10 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] ~f~%\"\n"
-      "        s5-10\n"
-      "        (-> (the-as (array float) arg0) s5-10)\n"
-      "        )\n"
+      "       (format #t \"~T  [~D] ~f~%\" s5-10 (-> (the-as (array float) arg0) s5-10))\n"
       "       (+! s5-10 1)\n"
       "       )\n"
       "      )\n"
-      "     (else\n"
-      "      (set! s5-11 0)\n"
+      "     )\n"
+      "    (else\n"
+      "     (let\n"
+      "      ((s5-11 0))\n"
       "      (while\n"
       "       (< s5-11 (-> arg0 length))\n"
-      "       (format\n"
-      "        #t\n"
-      "        \"~T  [~D] ~A~%\"\n"
-      "        s5-11\n"
-      "        (-> (the-as (array basic) arg0) s5-11)\n"
-      "        )\n"
+      "       (format #t \"~T  [~D] ~A~%\" s5-11 (-> (the-as (array basic) arg0) s5-11))\n"
       "       (+! s5-11 1)\n"
       "       )\n"
       "      )\n"
@@ -1919,13 +1914,13 @@ TEST_F(FormRegressionTest, ExprValid) {
   std::string type = "(function object type basic basic object symbol)";
 
   std::string expected =
-      "(begin\n"
-      "  (set!\n"
-      "   v1-1\n"
+      "(let\n"
+      "  ((v1-1\n"
       "    (and\n"
       "     (>= (the-as uint arg0) (the-as uint __START-OF-TABLE__))\n"
-      "     (< (the-as uint arg0) (the-as uint 134217728))\n"
+      "     (< (the-as uint arg0) (the-as uint #x8000000))\n"
       "     )\n"
+      "    )\n"
       "   )\n"
       "  (cond\n"
       "   ((not arg1)\n"
@@ -1933,24 +1928,24 @@ TEST_F(FormRegressionTest, ExprValid) {
       "     ((nonzero? (logand (the-as int arg0) 3))\n"
       "      (if\n"
       "       arg2\n"
-      "        (format\n"
-      "         arg4\n"
-      "         \"ERROR: object #x~X ~S is not a valid object (misaligned)~%\"\n"
-      "         arg0\n"
-      "         arg2\n"
-      "         )\n"
+      "       (format\n"
+      "        arg4\n"
+      "        \"ERROR: object #x~X ~S is not a valid object (misaligned)~%\"\n"
+      "        arg0\n"
+      "        arg2\n"
+      "        )\n"
       "       )\n"
       "      #f\n"
       "      )\n"
       "     ((not v1-1)\n"
       "      (if\n"
       "       arg2\n"
-      "        (format\n"
-      "         arg4\n"
-      "         \"ERROR: object #x~X ~S is not a valid object (bad address)~%\"\n"
-      "         arg0\n"
-      "         arg2\n"
-      "         )\n"
+      "       (format\n"
+      "        arg4\n"
+      "        \"ERROR: object #x~X ~S is not a valid object (bad address)~%\"\n"
+      "        arg0\n"
+      "        arg2\n"
+      "        )\n"
       "       )\n"
       "      #f\n"
       "      )\n"
@@ -1965,33 +1960,32 @@ TEST_F(FormRegressionTest, ExprValid) {
       "       ((nonzero? (logand (the-as int arg0) 15))\n"
       "        (if\n"
       "         arg2\n"
-      "          (format\n"
-      "           arg4\n"
-      "           \"ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%\"\n"
-      "           arg0\n"
-      "           arg2\n"
-      "           arg1\n"
-      "           )\n"
+      "         (format\n"
+      "          arg4\n"
+      "          \"ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%\"\n"
+      "          arg0\n"
+      "          arg2\n"
+      "          arg1\n"
+      "          )\n"
       "         )\n"
       "        #f\n"
       "        )\n"
       "       ((or\n"
       "         (not v1-1)\n"
       "         (begin\n"
-      "          (set! v1-10 32768)\n"
-      "          (.daddu v1-11 v1-10 s7-0)\n"
+      "          (let ((v1-10 #x8000)) (.daddu v1-11 v1-10 s7-0))\n"
       "          (< (the-as uint arg0) (the-as uint v1-11))\n"
       "          )\n"
       "         )\n"
       "        (if\n"
       "         arg2\n"
-      "          (format\n"
-      "           arg4\n"
-      "           \"ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%\"\n"
-      "           arg0\n"
-      "           arg2\n"
-      "           arg1\n"
-      "           )\n"
+      "         (format\n"
+      "          arg4\n"
+      "          \"ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%\"\n"
+      "          arg0\n"
+      "          arg2\n"
+      "          arg1\n"
+      "          )\n"
       "         )\n"
       "        #f\n"
       "        )\n"
@@ -2003,26 +1997,26 @@ TEST_F(FormRegressionTest, ExprValid) {
       "       ((!= (logand (the-as int arg0) 7) 2)\n"
       "        (if\n"
       "         arg2\n"
-      "          (format\n"
-      "           arg4\n"
-      "           \"ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%\"\n"
-      "           arg0\n"
-      "           arg2\n"
-      "           arg1\n"
-      "           )\n"
+      "         (format\n"
+      "          arg4\n"
+      "          \"ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%\"\n"
+      "          arg0\n"
+      "          arg2\n"
+      "          arg1\n"
+      "          )\n"
       "         )\n"
       "        #f\n"
       "        )\n"
       "       ((not v1-1)\n"
       "        (if\n"
       "         arg2\n"
-      "          (format\n"
-      "           arg4\n"
-      "           \"ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%\"\n"
-      "           arg0\n"
-      "           arg2\n"
-      "           arg1\n"
-      "           )\n"
+      "         (format\n"
+      "          arg4\n"
+      "          \"ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%\"\n"
+      "          arg0\n"
+      "          arg2\n"
+      "          arg1\n"
+      "          )\n"
       "         )\n"
       "        #f\n"
       "        )\n"
@@ -2035,13 +2029,13 @@ TEST_F(FormRegressionTest, ExprValid) {
       "       (else\n"
       "        (if\n"
       "         arg2\n"
-      "          (format\n"
-      "           arg4\n"
-      "           \"ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%\"\n"
-      "           arg0\n"
-      "           arg2\n"
-      "           arg1\n"
-      "           )\n"
+      "         (format\n"
+      "          arg4\n"
+      "          \"ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%\"\n"
+      "          arg0\n"
+      "          arg2\n"
+      "          arg1\n"
+      "          )\n"
       "         )\n"
       "        #f\n"
       "        )\n"
@@ -2050,94 +2044,89 @@ TEST_F(FormRegressionTest, ExprValid) {
       "     ((!= (logand (the-as int arg0) 7) 4)\n"
       "      (if\n"
       "       arg2\n"
-      "        (format\n"
-      "         arg4\n"
-      "         \"ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%\"\n"
-      "         arg0\n"
-      "         arg2\n"
-      "         arg1\n"
-      "         )\n"
+      "       (format\n"
+      "        arg4\n"
+      "        \"ERROR: object #x~X ~S is not a valid object of type '~A' (misaligned)~%\"\n"
+      "        arg0\n"
+      "        arg2\n"
+      "        arg1\n"
+      "        )\n"
       "       )\n"
       "      #f\n"
       "      )\n"
       "     ((not v1-1)\n"
       "      (if\n"
       "       arg2\n"
-      "        (format\n"
-      "         arg4\n"
-      "         \"ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%\"\n"
-      "         arg0\n"
-      "         arg2\n"
-      "         arg1\n"
-      "         )\n"
+      "       (format\n"
+      "        arg4\n"
+      "        \"ERROR: object #x~X ~S is not a valid object of type '~A' (bad address)~%\"\n"
+      "        arg0\n"
+      "        arg2\n"
+      "        arg1\n"
+      "        )\n"
       "       )\n"
       "      #f\n"
       "      )\n"
       "     ((and (= arg1 type) (!= (rtype-of arg0) type))\n"
       "      (if\n"
       "       arg2\n"
-      "        (format\n"
-      "         arg4\n"
-      "         \"ERROR: object #x~X ~S is not a valid object of type '~A' (invalid type "
-      "#x~X)~%\"\n"
-      "         arg0\n"
-      "         arg2\n"
-      "         arg1\n"
-      "         (rtype-of arg0)\n"
-      "         )\n"
+      "       (format\n"
+      "        arg4\n"
+      "        \"ERROR: object #x~X ~S is not a valid object of type '~A' (invalid type #x~X)~%\"\n"
+      "        arg0\n"
+      "        arg2\n"
+      "        arg1\n"
+      "        (rtype-of arg0)\n"
+      "        )\n"
       "       )\n"
       "      #f\n"
       "      )\n"
       "     (else\n"
       "      (cond\n"
-      "       ((and\t\n"
-      "         (!= arg1 type)\t\n"
-      "         (not (valid? (rtype-of arg0) type #f #t 0))\t\n"
-      "         )\n"
+      "       ((and (!= arg1 type) (not (valid? (rtype-of arg0) type #f #t 0)))\n"
       "        (if\n"
       "         arg2\n"
-      "          (format\n"
-      "           arg4\n"
-      "           \"ERROR: object #x~X ~S is not a valid object of type '~A' (invalid type "
+      "         (format\n"
+      "          arg4\n"
+      "          \"ERROR: object #x~X ~S is not a valid object of type '~A' (invalid type "
       "#x~X)~%\"\n"
-      "           arg0\n"
-      "           arg2\n"
-      "           arg1\n"
-      "           (rtype-of arg0)\n"
-      "           )\n"
+      "          arg0\n"
+      "          arg2\n"
+      "          arg1\n"
+      "          (rtype-of arg0)\n"
+      "          )\n"
       "         )\n"
       "        #f\n"
       "        )\n"
       "       ((not (type-type? (rtype-of arg0) arg1))\n"
       "        (if\n"
       "         arg2\n"
-      "          (format\n"
-      "           arg4\n"
-      "           \"ERROR: object #x~X ~S is not a valid object of type '~A' (is type '~A' "
+      "         (format\n"
+      "          arg4\n"
+      "          \"ERROR: object #x~X ~S is not a valid object of type '~A' (is type '~A' "
       "instead)~%\"\n"
-      "           arg0\n"
-      "           arg2\n"
-      "           arg1\n"
-      "           (rtype-of arg0)\n"
-      "           )\n"
+      "          arg0\n"
+      "          arg2\n"
+      "          arg1\n"
+      "          (rtype-of arg0)\n"
+      "          )\n"
       "         )\n"
       "        #f\n"
       "        )\n"
       "       ((= arg1 symbol)\n"
-      "        (set! v1-43 32768)\n"
-      "        (.daddu v1-44 v1-43 s7-0)\n"
+      "        (let ((v1-43 #x8000)) (.daddu v1-44 v1-43 s7-0))\n"
       "        (cond\n"
       "         ((>= (the-as uint arg0) (the-as uint v1-44))\n"
       "          (if\n"
       "           arg2\n"
-      "            (format\n"
-      "             arg4\n"
-      "             \"ERROR: object #x~X ~S is not a valid object of type '~A' (not in symbol "
+      "           (format\n"
+      "            arg4\n"
+      "            \"ERROR: object #x~X ~S is not a valid object of type '~A' (not in symbol "
       "table)~%\"\n"
-      "             arg0\n"
-      "             arg2\n"
-      "             arg1\n"
-      "             )\n"
+      "            arg0\n"
+      "            arg2\n"
+      "            arg1\n"
+      "            )\n"
       "           )\n"
       "          #f\n"
       "          )\n"
@@ -2145,20 +2134,19 @@ TEST_F(FormRegressionTest, ExprValid) {
       "         )\n"
       "        )\n"
       "       ((begin\n"
-      "         (set! v1-47 32768)\n"
-      "         (.daddu v1-48 v1-47 s7-0)\n"
+      "         (let ((v1-47 #x8000)) (.daddu v1-48 v1-47 s7-0))\n"
       "         (< (the-as uint arg0) (the-as uint v1-48))\n"
       "         )\n"
       "        (if\n"
       "         arg2\n"
-      "          (format\n"
-      "           arg4\n"
-      "           \"ERROR: object #x~X ~S is not a valid object of type '~A' (inside symbol "
+      "         (format\n"
+      "          arg4\n"
+      "          \"ERROR: object #x~X ~S is not a valid object of type '~A' (inside symbol "
       "table)~%\"\n"
-      "           arg0\n"
-      "           arg2\n"
-      "           arg1\n"
-      "           )\n"
+      "          arg0\n"
+      "          arg2\n"
+      "          arg1\n"
+      "          )\n"
       "         )\n"
       "        #f\n"
       "        )\n"
@@ -2465,101 +2453,97 @@ TEST_F(FormRegressionTest, ExprStringToInt) {
   std::string type = "(function string int)";
   std::string expected =
       "(defun test-function ((arg0 string))\n"
-      "  (local-vars\n"
-      "   (v0-0 int)\n"
-      "   (v1-0 symbol)\n"
-      "   (a0-1 (pointer uint8))\n"
-      "   (a0-2 (pointer uint8))\n"
-      "   (a0-3 (pointer uint8))\n"
-      "   (a0-4 (pointer uint8))\n"
-      "   (a1-8 (pointer uint8))\n"
-      "   (a1-14 uint)\n"
-      "   (a1-20 uint)\n"
-      "   (a1-23 uint)\n"
-      "   (a1-47 (pointer uint8))\n"
-      "   )\n"
-      "  (set! a0-1 (-> arg0 data))\n"
-      "  (set! v0-0 0)\n"
-      "  (set! v1-0 #f)\n"
-      "  (cond\n"
-      "   ((= (-> a0-1 0) 35)\n"
-      "    (set! a0-2 (&-> a0-1 1))\n"
-      "    (cond\n"
-      "     ((or (= (-> a0-2 0) 120) (=  (-> a0-2 0) 88))\n"
-      "      (set! a0-3 (&-> a0-2 1))\n"
-      "      (when\n"
-      "       (= (-> a0-3 1) 45)\n"
-      "       (set! v1-0 #t)\n"
-      "       (set! a0-3 (&-> a0-3 1))\n"
-      "       (set! a1-8 a0-3)\n"
-      "       )\n"
-      "      (while\n"
-      "       (or\n"
-      "        (and\n"
-      "         (>= (-> a0-3 0) (the-as uint 48))\n"
-      "         (>= (the-as uint 57) (-> a0-3 0))\n"
-      "         )\n"
-      "        (and\n"
-      "         (>= (-> a0-3 0) (the-as uint 65))\n"
-      "         (>= (the-as uint 70) (-> a0-3 0))\n"
-      "         )\n"
-      "        (and\n"
-      "         (>= (-> a0-3 0) (the-as uint 97))\n"
-      "         (>= (the-as uint 102) (-> a0-3 0))\n"
-      "         )\n"
-      "        )\n"
-      "       (cond\n"
-      "        ((and\n"
-      "          (>= (-> a0-3 0) (the-as uint 65))\n"
-      "          (>= (the-as uint 70) (-> a0-3 0))\n"
+      "  (let\n"
+      "   ((a0-1 (-> arg0 data)) (v0-0 0) (v1-0 #f))\n"
+      "   (cond\n"
+      "    ((= (-> a0-1 0) 35)\n"
+      "     (let\n"
+      "      ((a0-2 (&-> a0-1 1)))\n"
+      "      (cond\n"
+      "       ((or (= (-> a0-2 0) 120) (= (-> a0-2 0) 88))\n"
+      "        (let\n"
+      "         ((a0-3 (&-> a0-2 1)))\n"
+      "         (when\n"
+      "          (= (-> a0-3 1) 45)\n"
+      "          (set! v1-0 #t)\n"
+      "          (set! a0-3 (&-> a0-3 1))\n"
+      "          (let ((a1-8 a0-3)))\n"
       "          )\n"
-      "         (set! v0-0 (+ (+ (-> a0-3 0) -55) (the-as uint (shl v0-0 4))))\n"
-      "         (set! a1-14 v0-0)\n"
-      "         )\n"
-      "        (else\n"
-      "         (cond\n"
-      "          ((and\t\n"
-      "            (>= (-> a0-3 0) (the-as uint 97))\t\n"
-      "            (>= (the-as uint 102) (-> a0-3 0))\t\n"
+      "         (while\n"
+      "          (or\n"
+      "           (and\n"
+      "            (>= (-> a0-3 0) (the-as uint 48))\n"
+      "            (>= (the-as uint 57) (-> a0-3 0))\n"
+      "            )\n"
+      "           (and\n"
+      "            (>= (-> a0-3 0) (the-as uint 65))\n"
+      "            (>= (the-as uint 70) (-> a0-3 0))\n"
+      "            )\n"
+      "           (and\n"
+      "            (>= (-> a0-3 0) (the-as uint 97))\n"
+      "            (>= (the-as uint 102) (-> a0-3 0))\n"
       "            )\n"
-      "           (set! v0-0 (+ (+ (-> a0-3 0) -87) (the-as uint (shl v0-0 4))))\n"
-      "           (set! a1-20 v0-0)\n"
       "           )\n"
-      "          (else\n"
-      "           (set! v0-0 (+ (+ (-> a0-3 0) -48) (the-as uint (shl v0-0 4))))\n"
-      "           (set! a1-23 v0-0)\n"
+      "          (cond\n"
+      "           ((and\n"
+      "             (>= (-> a0-3 0) (the-as uint 65))\n"
+      "             (>= (the-as uint 70) (-> a0-3 0))\n"
+      "             )\n"
+      "            (set! v0-0 (+ (+ (-> a0-3 0) -55) (the-as uint (shl v0-0 4))))\n"
+      "            (let ((a1-14 v0-0)))\n"
+      "            )\n"
+      "           (else\n"
+      "            (cond\n"
+      "             ((and\n"
+      "               (>= (-> a0-3 0) (the-as uint 97))\n"
+      "               (>= (the-as uint 102) (-> a0-3 0))\n"
+      "               )\n"
+      "              (set! v0-0 (+ (+ (-> a0-3 0) -87) (the-as uint (shl v0-0 4))))\n"
+      "              (let ((a1-20 v0-0)))\n"
+      "              )\n"
+      "             (else\n"
+      "              (set! v0-0 (+ (+ (-> a0-3 0) -48) (the-as uint (shl v0-0 4))))\n"
+      "              (let ((a1-23 v0-0)))\n"
+      "              )\n"
+      "             )\n"
+      "            )\n"
       "           )\n"
+      "          (set! a0-3 (&-> a0-3 1))\n"
+      "          )\n"
+      "         )\n"
+      "        )\n"
+      "       ((or (= (-> a0-2 0) 98) (= (-> a0-2 0) 66))\n"
+      "        (let\n"
+      "         ((a0-4 (&-> a0-2 1)))\n"
+      "         (while\n"
+      "          (and\n"
+      "           (>= (-> a0-4 0) (the-as uint 48))\n"
+      "           (>= (the-as uint 49) (-> a0-4 0))\n"
+      "           )\n"
+      "          (set! v0-0 (+ (+ (-> a0-4 0) -48) (the-as uint (shl v0-0 1))))\n"
+      "          (set! a0-4 (&-> a0-4 1))\n"
       "          )\n"
       "         )\n"
       "        )\n"
-      "       (set! a0-3 (&-> a0-3 1))\n"
-      "       )\n"
-      "      )\n"
-      "     ((or (= (-> a0-2 0) 98) (= (-> a0-2 0) 66))\n"
-      "      (set! a0-4 (&-> a0-2 1))\n"
-      "      (while\n"
-      "       (and (>= (-> a0-4 0) (the-as uint 48)) (>= (the-as uint 49) (-> a0-4 0)))\n"
-      "       (set! v0-0 (+ (+ (-> a0-4 0) -48) (the-as uint (shl v0-0 1))))\n"
-      "       (set! a0-4 (&-> a0-4 1))\n"
       "       )\n"
       "      )\n"
       "     )\n"
-      "    )\n"
-      "   (else\n"
-      "    (when\n"
-      "     (= (-> a0-1 1) 45)\n"
-      "     (set! v1-0 #t)\n"
-      "     (set! a0-1 (&-> a0-1 1))\n"
-      "     (set! a1-47 a0-1)\n"
-      "     )\n"
-      "    (while\n"
-      "     (and (>= (-> a0-1 0) (the-as uint 48)) (>= (the-as uint 57) (-> a0-1 0)))\n"
-      "     (set! v0-0 (+ (+ (-> a0-1 0) -48) (the-as uint (* 10 v0-0))))\n"
-      "     (set! a0-1 (&-> a0-1 1))\n"
+      "    (else\n"
+      "     (when\n"
+      "      (= (-> a0-1 1) 45)\n"
+      "      (set! v1-0 #t)\n"
+      "      (set! a0-1 (&-> a0-1 1))\n"
+      "      (let ((a1-47 a0-1)))\n"
+      "      )\n"
+      "     (while\n"
+      "      (and (>= (-> a0-1 0) (the-as uint 48)) (>= (the-as uint 57) (-> a0-1 0)))\n"
+      "      (set! v0-0 (+ (+ (-> a0-1 0) -48) (the-as uint (* 10 v0-0))))\n"
+      "      (set! a0-1 (&-> a0-1 1))\n"
+      "      )\n"
       "     )\n"
       "    )\n"
+      "   (cond (v1-0 (- v0-0)) (else (empty) v0-0))\n"
       "   )\n"
-      "  (cond (v1-0 (- v0-0)) (else (empty) v0-0))\n"
       "  )";
   test_final_function(func, type, expected);
 }
diff --git a/test/decompiler/test_gkernel_decomp.cpp b/test/decompiler/test_gkernel_decomp.cpp
index d5a579cf7..bb1539477 100644
--- a/test/decompiler/test_gkernel_decomp.cpp
+++ b/test/decompiler/test_gkernel_decomp.cpp
@@ -62,10 +62,12 @@ TEST_F(FormRegressionTest, ExprLoadPackage) {
   std::string expected =
       "(when\n"
       "  (not (nmember arg0 *kernel-packages*))\n"
-      "  (dgo-load arg0 arg1 15 2097152)\n"
-      "  (set! v0-1 (cons arg0 *kernel-packages*))\n"
-      "  (set! *kernel-packages* v0-1)\n"
-      "  v0-1\n"
+      "  (dgo-load arg0 arg1 15 #x200000)\n"
+      "  (let\n"
+      "   ((v0-1 (cons arg0 *kernel-packages*)))\n"
+      "   (set! *kernel-packages* v0-1)\n"
+      "   v0-1\n"
+      "   )\n"
       "  )";
   test_with_expr(func, type, expected);
 }
@@ -100,8 +102,10 @@ TEST_F(FormRegressionTest, ExprUnloadPackage) {
   std::string type = "(function string pair)";
   std::string expected =
       "(begin\n"
-      "  (set! v1-0 (nmember arg0 *kernel-packages*))\n"
-      "  (if v1-0 (set! *kernel-packages* (delete! (car v1-0) *kernel-packages*)))\n"
+      "  (let\n"
+      "   ((v1-0 (nmember arg0 *kernel-packages*)))\n"
+      "   (if v1-0 (set! *kernel-packages* (delete! (car v1-0) *kernel-packages*)))\n"
+      "   )\n"
       "  *kernel-packages*\n"
       "  )";
   test_with_expr(func, type, expected, true);
@@ -128,7 +132,7 @@ TEST_F(FormRegressionTest, ExprMethod1Thread) {
   std::string type = "(function thread none)";
   std::string expected =
       "(begin\n"
-      "  (when (= arg0 (-> arg0 process main-thread)) (break!) (set! v1-3 0))\n"
+      "  (when (= arg0 (-> arg0 process main-thread)) (break!) (let ((v1-3 0))))\n"
       "  (set! (-> arg0 process top-thread) (-> arg0 previous))\n"
       "  )";
   test_with_expr(func, type, expected, false);
@@ -253,26 +257,28 @@ TEST_F(FormRegressionTest, ExprMethod9Thread) {
   std::string type = "(function thread int none)";
   std::string expected =
       "(begin\n"
-      "  (set! a2-0 (-> arg0 process))\n"
-      "  (cond\n"
-      "   ((!= arg0 (-> a2-0 main-thread)) (format 0 \"1 ~A ~%\" a2-0))\n"
-      "   ((= (-> arg0 stack-size) arg1))\n"
-      "   ((=\n"
-      "     (-> a2-0 heap-cur)\n"
-      "     (+\n"
-      "      (+ (+ (-> arg0 stack-size) -4) (the-as int (-> arg0 type size)))\n"
-      "      (the-as int arg0)\n"
+      "  (let\n"
+      "   ((a2-0 (-> arg0 process)))\n"
+      "   (cond\n"
+      "    ((!= arg0 (-> a2-0 main-thread)) (format 0 \"1 ~A ~%\" a2-0))\n"
+      "    ((= (-> arg0 stack-size) arg1))\n"
+      "    ((=\n"
+      "      (-> a2-0 heap-cur)\n"
+      "      (+\n"
+      "       (+ (+ (-> arg0 stack-size) -4) (the-as int (-> arg0 type size)))\n"
+      "       (the-as int arg0)\n"
+      "       )\n"
       "      )\n"
+      "     (set!\n"
+      "      (-> a2-0 heap-cur)\n"
+      "      (+ (+ (+ arg1 -4) (the-as int (-> arg0 type size))) (the-as int arg0))\n"
+      "      )\n"
+      "     (set! (-> arg0 stack-size) arg1)\n"
       "     )\n"
-      "    (set!\n"
-      "     (-> a2-0 heap-cur)\n"
-      "     (+ (+ (+ arg1 -4) (the-as int (-> arg0 type size))) (the-as int arg0))\n"
-      "     )\n"
-      "    (set! (-> arg0 stack-size) arg1)\n"
+      "    (else (format 0 \"2 ~A ~%\" a2-0))\n"
       "    )\n"
-      "   (else (format 0 \"2 ~A ~%\" a2-0))\n"
       "   )\n"
-      "  (set! v0-2 0)\n"
+      "  (let ((v0-2 0)))\n"
       "  )";
   test_with_expr(func, type, expected, false, "", {{"L342", "1 ~A ~%"}, {"L341", "2 ~A ~%"}});
 }
@@ -319,18 +325,16 @@ TEST_F(FormRegressionTest, ExprMethod0Thread) {
       "    daddu sp, sp, r0";
   std::string type = "(function symbol type process symbol int pointer thread)";
   std::string expected =
-      "(begin\n"
-      "  (set!\n"
-      "   v0-0\n"
-      "   (cond\n"
-      "    ((-> arg2 top-thread) (&+ arg5 -7164))\n"
-      "    (else\n"
-      "     (set!\n"
-      "      v1-2\n"
-      "      (logand -16 (the-as int (&+ (-> arg2 heap-cur) 15)))\n"
+      "(let\n"
+      "  ((v0-0\n"
+      "    (if\n"
+      "     (-> arg2 top-thread)\n"
+      "     (&+ arg5 -7164)\n"
+      "     (let\n"
+      "      ((v1-2 (logand -16 (the-as int (&+ (-> arg2 heap-cur) 15)))))\n"
+      "      (set! (-> arg2 heap-cur) (+ (+ v1-2 (the-as int (-> arg1 size))) arg4))\n"
+      "      (+ v1-2 4)\n"
       "      )\n"
-      "     (set! (-> arg2 heap-cur) (+ (+ v1-2 (the-as int (-> arg1 size))) arg4))\n"
-      "     (+ v1-2 4)\n"
       "     )\n"
       "    )\n"
       "   )\n"
@@ -341,7 +345,6 @@ TEST_F(FormRegressionTest, ExprMethod0Thread) {
       "  (set! (-> v0-0 stack-top) arg5)\n"
       "  (set! (-> v0-0 previous) (-> arg2 top-thread))\n"
       "  (set! (-> arg2 top-thread) v0-0)\n"
-      // TODO - we could make this method access nicer.
       "  (set! (-> v0-0 suspend-hook) (method-of-object v0-0 thread-suspend))\n"
       "  (set! (-> v0-0 resume-hook) (method-of-object v0-0 thread-resume))\n"
       "  (set! (-> v0-0 stack-size) arg4)\n"
@@ -383,11 +386,13 @@ TEST_F(FormRegressionTest, RemoveExit) {
       "    daddu sp, sp, r0";
   std::string type = "(function stack-frame)";
   std::string expected =
-      "(when\n"
+      "(if\n"
       "  (-> pp stack-frame-top)\n"
-      "  (set! v0-0 (-> pp stack-frame-top next))\n"
-      "  (set! (-> pp stack-frame-top) v0-0)\n"
-      "  v0-0\n"
+      "  (let\n"
+      "   ((v0-0 (-> pp stack-frame-top next)))\n"
+      "   (set! (-> pp stack-frame-top) v0-0)\n"
+      "   v0-0\n"
+      "   )\n"
       "  )";
   test_with_expr(func, type, expected, false);
 }
@@ -423,8 +428,8 @@ TEST_F(FormRegressionTest, RemoveMethod0ProcessTree) {
       "    daddiu sp, sp, 32";
   std::string type = "(function symbol type basic process-tree)";
   std::string expected =
-      "(begin\n"
-      "  (set! v0-0 (object-new arg0 arg1 (the-as int (-> arg1 size))))\n"
+      "(let\n"
+      "  ((v0-0 (object-new arg0 arg1 (the-as int (-> arg1 size)))))\n"
       "  (set! (-> v0-0 name) arg2)\n"
       "  (set! (-> v0-0 mask) 256)\n"
       "  (set! (-> v0-0 parent) #f)\n"
@@ -525,21 +530,18 @@ TEST_F(FormRegressionTest, RemoveMethod3ProcessTree) {
       "  (format #t \"[~8x] ~A~%\" arg0 (-> arg0 type))\n"
       "  (format #t \"~Tname: ~S~%\" (-> arg0 name))\n"
       "  (format #t \"~Tmask: #x~X~%\" (-> arg0 mask))\n"
-      "  (set! t9-3 format)\n"
-      "  (set! a0-4 #t)\n"
-      "  (set! a1-3 \"~Tparent: ~A~%\")\n"
-      "  (set! v1-0 (-> arg0 parent))\n"
-      "  (t9-3 a0-4 a1-3 (if v1-0 (-> v1-0 0 self)))\n"
-      "  (set! t9-4 format)\n"
-      "  (set! a0-5 #t)\n"
-      "  (set! a1-4 \"~Tbrother: ~A~%\")\n"
-      "  (set! v1-2 (-> arg0 brother))\n"
-      "  (t9-4 a0-5 a1-4 (if v1-2 (-> v1-2 0 self)))\n"
-      "  (set! t9-5 format)\n"
-      "  (set! a0-6 #t)\n"
-      "  (set! a1-5 \"~Tchild: ~A~%\")\n"
-      "  (set! v1-4 (-> arg0 child))\n"
-      "  (t9-5 a0-6 a1-5 (if v1-4 (-> v1-4 0 self)))\n"
+      "  (let\n"
+      "   ((t9-3 format) (a0-4 #t) (a1-3 \"~Tparent: ~A~%\") (v1-0 (-> arg0 parent)))\n"
+      "   (t9-3 a0-4 a1-3 (if v1-0 (-> v1-0 0 self)))\n"
+      "   )\n"
+      "  (let\n"
+      "   ((t9-4 format) (a0-5 #t) (a1-4 \"~Tbrother: ~A~%\") (v1-2 (-> arg0 brother)))\n"
+      "   (t9-4 a0-5 a1-4 (if v1-2 (-> v1-2 0 self)))\n"
+      "   )\n"
+      "  (let\n"
+      "   ((t9-5 format) (a0-6 #t) (a1-5 \"~Tchild: ~A~%\") (v1-4 (-> arg0 child)))\n"
+      "   (t9-5 a0-6 a1-5 (if v1-4 (-> v1-4 0 self)))\n"
+      "   )\n"
       "  arg0\n"
       "  )";
   test_with_expr(func, type, expected, false, "process-tree",
@@ -619,13 +621,17 @@ TEST_F(FormRegressionTest, ExprMethod0Process) {
       "    daddiu sp, sp, 48";
   std::string type = "(function symbol type basic int process)";
   std::string expected =
-      "(begin\n"
-      "  (set!\n"
-      "   v0-0\n"
-      "   (if\n"
-      "    (= (-> arg0 type) symbol)\n"
-      "    (object-new arg0 arg1 (the-as int (+ (-> process size) (the-as uint arg3))))\n"
-      "    (+ (the-as int arg0) 4)\n"
+      "(let\n"
+      "  ((v0-0\n"
+      "    (if\n"
+      "     (= (-> arg0 type) symbol)\n"
+      "     (object-new\n"
+      "      arg0\n"
+      "      arg1\n"
+      "      (the-as int (+ (-> process size) (the-as uint arg3)))\n"
+      "      )\n"
+      "     (+ (the-as int arg0) 4)\n"
+      "     )\n"
       "    )\n"
       "   )\n"
       "  (set! (-> (the-as process v0-0) name) arg2)\n"
@@ -635,9 +641,11 @@ TEST_F(FormRegressionTest, ExprMethod0Process) {
       "  (set! (-> v0-0 allocated-length) arg3)\n"
       "  (set! (-> v0-0 top-thread) #f)\n"
       "  (set! (-> v0-0 main-thread) #f)\n"
-      "  (set! v1-5 (-> v0-0 stack))\n"
-      "  (set! (-> v0-0 heap-cur) v1-5)\n"
-      "  (set! (-> v0-0 heap-base) v1-5)\n"
+      "  (let\n"
+      "   ((v1-5 (-> v0-0 stack)))\n"
+      "   (set! (-> v0-0 heap-cur) v1-5)\n"
+      "   (set! (-> v0-0 heap-base) v1-5)\n"
+      "   )\n"
       "  (set! (-> v0-0 heap-top) (&-> v0-0 stack (-> v0-0 allocated-length)))\n"
       "  (set! (-> v0-0 stack-frame-top) (-> v0-0 heap-top))\n"
       "  (set! (-> v0-0 stack-frame-top) #f)\n"
@@ -711,15 +719,16 @@ TEST_F(FormRegressionTest, ExprInspectProcessHeap) {
   std::string type = "(function process symbol)";
   std::string expected =
       "(begin\n"
-      "  (set! s5-0 (&+ (-> arg0 heap-base) 4))\n"
-      "  (while\n"
-      "   (< (the-as int s5-0) (the-as int (-> arg0 heap-cur)))\n"
-      "   (inspect (the-as basic s5-0))\n"
-      "   (+! (the-as int s5-0) (logand -16 (+ (asize-of s5-0) 15)))\n"
+      "  (let\n"
+      "   ((s5-0 (&+ (-> arg0 heap-base) 4)))\n"
+      "   (while\n"
+      "    (< (the-as int s5-0) (the-as int (-> arg0 heap-cur)))\n"
+      "    (inspect (the-as basic s5-0))\n"
+      "    (+! (the-as int s5-0) (logand -16 (+ (asize-of s5-0) 15)))\n"
+      "    )\n"
       "   )\n"
       "  #f\n"
-      "  )\n"
-      "";
+      "  )";
   test_with_expr(func, type, expected, false, "", {},
                  parse_hint_json("[\t\t[4, [\"s5\", \"basic\"]],\n"
                                  "\t\t[17, [\"s5\", \"int\"]]]"));
@@ -914,8 +923,8 @@ TEST_F(FormRegressionTest, ExprMethod0DeadPool) {
       "    daddiu sp, sp, 112";
   std::string type = "(function symbol type int int basic dead-pool)";
   std::string expected =
-      "(begin\n"
-      "  (set! s3-0 (object-new arg0 arg1 (the-as int (-> arg1 size))))\n"
+      "(let\n"
+      "  ((s3-0 (object-new arg0 arg1 (the-as int (-> arg1 size)))))\n"
       "  (set! (-> s3-0 name) arg4)\n"
       "  (set! (-> s3-0 mask) 256)\n"
       "  (set! (-> s3-0 parent) #f)\n"
@@ -923,18 +932,21 @@ TEST_F(FormRegressionTest, ExprMethod0DeadPool) {
       "  (set! (-> s3-0 child) #f)\n"
       "  (set! (-> s3-0 self) s3-0)\n"
       "  (set! (-> s3-0 ppointer) (&-> s3-0 self))\n"
-      "  (set! s2-1 0)\n"
-      "  (while\n"
-      "   (< s2-1 arg2)\n"
-      "   (set! s1-0 (-> s3-0 child))\n"
-      "   (set! v1-5 ((method-of-type process new) arg0 process (quote dead) arg3))\n"
-      "   (set! a0-3 v1-5)\n"
-      "   (set! (-> s3-0 child) (if a0-3 (-> a0-3 ppointer)))\n"
-      "   (set! a0-4 s3-0)\n"
-      "   (set! (-> v1-5 parent) (if a0-4 (-> a0-4 ppointer)))\n"
-      "   (set! (-> v1-5 pool) s3-0)\n"
-      "   (set! (-> v1-5 brother) s1-0)\n"
-      "   (+! s2-1 1)\n"
+      "  (let\n"
+      "   ((s2-1 0))\n"
+      "   (while\n"
+      "    (< s2-1 arg2)\n"
+      "    (let\n"
+      "     ((s1-0 (-> s3-0 child))\n"
+      "      (v1-5 ((method-of-type process new) arg0 process (quote dead) arg3))\n"
+      "      )\n"
+      "     (let ((a0-3 v1-5)) (set! (-> s3-0 child) (if a0-3 (-> a0-3 ppointer))))\n"
+      "     (let ((a0-4 s3-0)) (set! (-> v1-5 parent) (if a0-4 (-> a0-4 ppointer))))\n"
+      "     (set! (-> v1-5 pool) s3-0)\n"
+      "     (set! (-> v1-5 brother) s1-0)\n"
+      "     )\n"
+      "    (+! s2-1 1)\n"
+      "    )\n"
       "   )\n"
       "  s3-0\n"
       "  )";
@@ -1039,28 +1051,31 @@ TEST_F(FormRegressionTest, ExprMethod14DeadPool) {
       "    jr ra\n"
       "    daddiu sp, sp, 64";
   std::string type = "(function dead-pool type int process)";
+  // todo - why does one work but not the other??
   std::string expected =
-      "(begin\n"
-      "  (set! s4-0 (-> arg0 child))\n"
+      "(let\n"
+      "  ((s4-0 (-> arg0 child)))\n"
       "  (when\n"
       "   (and (not s4-0) *debug-segment* (!= arg0 *debug-dead-pool*))\n"
       "   (set! s4-0 (get-process *debug-dead-pool* arg1 arg2))\n"
-      "   (when\n"
+      "   (if\n"
       "    s4-0\n"
-      "    (set! t9-1 format)\n"
-      "    (set! a0-2 0)\n"
-      "    (set!\n"
-      "     a1-2\n"
-      "     \"WARNING: ~A ~A had to be allocated from the debug pool, because ~A was empty.~%\"\n"
-      "     )\n"
-      "    (set! a2-1 arg1)\n"
-      "    (set! v1-6 s4-0)\n"
-      "    (t9-1\n"
-      "     a0-2\n"
-      "     a1-2\n"
-      "     a2-1\n"
-      "     (if v1-6 (-> (the-as (pointer process-tree) v1-6) 0 self))\n"
-      "     (-> arg0 name)\n"
+      "    (let\n"
+      "     ((t9-1 format)\n"
+      "      (a0-2 0)\n"
+      "      (a1-2\n"
+      "       \"WARNING: ~A ~A had to be allocated from the debug pool, because ~A was empty.~%\"\n"
+      "       )\n"
+      "      (a2-1 arg1)\n"
+      "      (v1-6 s4-0)\n"
+      "      )\n"
+      "     (t9-1\n"
+      "      a0-2\n"
+      "      a1-2\n"
+      "      a2-1\n"
+      "      (if v1-6 (-> (the-as (pointer process-tree) v1-6) 0 self))\n"
+      "      (-> arg0 name)\n"
+      "      )\n"
       "     )\n"
       "    )\n"
       "   )\n"
@@ -1214,17 +1229,17 @@ TEST_F(FormRegressionTest, ExprMethod0DeadPoolHeap) {
       "    daddiu sp, sp, 64";
   std::string type = "(function symbol type basic int int dead-pool-heap)";
   std::string expected =
-      "(begin\n"
-      "  (set!\n"
-      "   v0-0\n"
-      "   (object-new\n"
-      "    arg0\n"
-      "    arg1\n"
-      "    (the-as\n"
-      "     int\n"
-      "     (+\n"
-      "      (+ (-> arg1 size) (the-as uint (logand -16 (+ (* 12 arg3) 15))))\n"
-      "      (the-as uint arg4)\n"
+      "(let\n"
+      "  ((v0-0\n"
+      "    (object-new\n"
+      "     arg0\n"
+      "     arg1\n"
+      "     (the-as\n"
+      "      int\n"
+      "      (+\n"
+      "       (+ (-> arg1 size) (the-as uint (logand -16 (+ (* 12 arg3) 15))))\n"
+      "       (the-as uint arg4)\n"
+      "       )\n"
       "      )\n"
       "     )\n"
       "    )\n"
@@ -1237,13 +1252,17 @@ TEST_F(FormRegressionTest, ExprMethod0DeadPoolHeap) {
       "  (set! (-> v0-0 child) #f)\n"
       "  (set! (-> v0-0 self) v0-0)\n"
       "  (set! (-> v0-0 ppointer) (&-> v0-0 self))\n"
-      "  (set! v1-4 arg3)\n"
-      "  (while\n"
-      "   (nonzero? v1-4)\n"
-      "   (+! v1-4 -1)\n"
-      "   (set! a0-4 (-> v0-0 process-list v1-4))\n"
-      "   (set! (-> a0-4 process) *null-process*)\n"
-      "   (set! (-> a0-4 next) (-> v0-0 process-list (+ v1-4 1)))\n"
+      "  (let\n"
+      "   ((v1-4 arg3))\n"
+      "   (while\n"
+      "    (nonzero? v1-4)\n"
+      "    (+! v1-4 -1)\n"
+      "    (let\n"
+      "     ((a0-4 (-> v0-0 process-list v1-4)))\n"
+      "     (set! (-> a0-4 process) *null-process*)\n"
+      "     (set! (-> a0-4 next) (-> v0-0 process-list (+ v1-4 1)))\n"
+      "     )\n"
+      "    )\n"
       "   )\n"
       "  (set! (-> v0-0 dead-list next) (-> v0-0 process-list))\n"
       "  (set! (-> v0-0 alive-list process) #f)\n"
@@ -1255,10 +1274,7 @@ TEST_F(FormRegressionTest, ExprMethod0DeadPoolHeap) {
       "  (set! (-> v0-0 first-shrink) #f)\n"
       "  (set!\n"
       "   (-> v0-0 heap base)\n"
-      "   (logand\n"
-      "    -16\n"
-      "    (the-as int (&+ (+ (the-as int v0-0) 115) (* 12 arg3)))\n"
-      "    )\n"
+      "   (logand -16 (the-as int (&+ (+ (the-as int v0-0) 115) (* 12 arg3))))\n"
       "   )\n"
       "  (set! (-> v0-0 heap current) (-> v0-0 heap base))\n"
       "  (set! (-> v0-0 heap top) (&+ (-> v0-0 heap base) arg4))\n"
@@ -1364,13 +1380,14 @@ TEST_F(FormRegressionTest, ExprMethod21DeadPoolHeap) {
       "    daddu sp, sp, r0";
   std::string type = "(function dead-pool-heap dead-pool-heap-rec int)";
   std::string expected =
-      "(cond\n"
-      "  ((-> arg1 process)\n"
-      "   (set!\n"
-      "    v1-3\n"
-      "    (&+\n"
-      "     (&+ (-> arg1 process) (-> process size))\n"
-      "     (-> arg1 process allocated-length)\n"
+      "(if\n"
+      "  (-> arg1 process)\n"
+      "  (let\n"
+      "   ((v1-3\n"
+      "     (&+\n"
+      "      (&+ (-> arg1 process) (-> process size))\n"
+      "      (-> arg1 process allocated-length)\n"
+      "      )\n"
       "     )\n"
       "    )\n"
       "   (if\n"
@@ -1379,15 +1396,10 @@ TEST_F(FormRegressionTest, ExprMethod21DeadPoolHeap) {
       "    (- (-> arg0 heap top) (the-as uint (&+ v1-3 4)))\n"
       "    )\n"
       "   )\n"
-      "  (else\n"
-      "   (if\n"
-      "    (-> arg1 next)\n"
-      "    (-\n"
-      "     (-> arg1 next process)\n"
-      "     (the-as uint (&+ (-> arg0 heap base) 4))\n"
-      "     )\n"
-      "    (- (-> arg0 heap top) (the-as uint (-> arg0 heap base)))\n"
-      "    )\n"
+      "  (if\n"
+      "   (-> arg1 next)\n"
+      "   (- (-> arg1 next process) (the-as uint (&+ (-> arg0 heap base) 4)))\n"
+      "   (- (-> arg0 heap top) (the-as uint (-> arg0 heap base)))\n"
       "   )\n"
       "  )";
   test_with_expr(func, type, expected, false, "", {},
@@ -1524,44 +1536,48 @@ TEST_F(FormRegressionTest, ExprMethod3DeadPoolHeap) {
   std::string type = "(function dead-pool-heap dead-pool-heap)";
   std::string expected =
       "(begin\n"
-      "  (set! s5-0 (- (-> arg0 heap top) (the-as uint (-> arg0 heap base))))\n"
-      "  (set!\n"
-      "   v1-3\n"
-      "   (if (-> arg0 alive-list prev) (gap-size arg0 (-> arg0 alive-list prev)) s5-0)\n"
+      "  (let*\n"
+      "   ((s5-0 (- (-> arg0 heap top) (the-as uint (-> arg0 heap base))))\n"
+      "    (v1-3\n"
+      "     (if\n"
+      "      (-> arg0 alive-list prev)\n"
+      "      (gap-size arg0 (-> arg0 alive-list prev))\n"
+      "      s5-0\n"
+      "      )\n"
+      "     )\n"
+      "    )\n"
+      "   (format\n"
+      "    #t\n"
+      "    \"~Tprocess-list[0] @ #x~X     ~D/~D bytes used~%\"\n"
+      "    (-> arg0 process-list)\n"
+      "    (- s5-0 v1-3)\n"
+      "    s5-0\n"
+      "    )\n"
       "   )\n"
-      "  (format\n"
-      "   #t\n"
-      "   \"~Tprocess-list[0] @ #x~X     ~D/~D bytes used~%\"\n"
-      "   (-> arg0 process-list)\n"
-      "   (- s5-0 v1-3)\n"
-      "   s5-0\n"
-      "   )\n"
-      "  (set! s5-1 (-> arg0 alive-list))\n"
-      "  (set! s4-0 0)\n"
-      "  (while\n"
-      "   s5-1\n"
-      "   (if\n"
-      "    (-> s5-1 process)\n"
-      "    (format\n"
-      "     #t\n"
-      "     \"~T  [~3D] #<dead-pool-heap-rec @ #x~X>  ~A~%\"\n"
-      "     s4-0\n"
-      "     s5-1\n"
+      "  (let\n"
+      "   ((s5-1 (-> arg0 alive-list)) (s4-0 0))\n"
+      "   (while\n"
+      "    s5-1\n"
+      "    (if\n"
       "     (-> s5-1 process)\n"
+      "     (format\n"
+      "      #t\n"
+      "      \"~T  [~3D] #<dead-pool-heap-rec @ #x~X>  ~A~%\"\n"
+      "      s4-0\n"
+      "      s5-1\n"
+      "      (-> s5-1 process)\n"
+      "      )\n"
       "     )\n"
-      "    )\n"
-      "   (set! s3-0 (gap-size arg0 s5-1))\n"
-      "   (if\n"
-      "    (nonzero? s3-0)\n"
-      "    (format\n"
-      "     #t\n"
-      "     \"~T   gap: ~D bytes @ #x~X~%\"\n"
-      "     s3-0\n"
-      "     (gap-location arg0 s5-1)\n"
+      "    (let\n"
+      "     ((s3-0 (gap-size arg0 s5-1)))\n"
+      "     (if\n"
+      "      (nonzero? s3-0)\n"
+      "      (format #t \"~T   gap: ~D bytes @ #x~X~%\" s3-0 (gap-location arg0 s5-1))\n"
+      "      )\n"
       "     )\n"
+      "    (set! s5-1 (-> s5-1 next))\n"
+      "    (+! s4-0 1)\n"
       "    )\n"
-      "   (set! s5-1 (-> s5-1 next))\n"
-      "   (+! s4-0 1)\n"
       "   )\n"
       "  arg0\n"
       "  )";
@@ -1683,8 +1699,8 @@ TEST_F(FormRegressionTest, ExprMethod25DeadPoolHeap) {
       "    daddiu sp, sp, 16";
   std::string type = "(function dead-pool-heap int)";
   std::string expected =
-      "(begin\n"
-      "  (set! v1-0 (-> arg0 heap top))\n"
+      "(let\n"
+      "  ((v1-0 (-> arg0 heap top)))\n"
       "  (if\n"
       "   (-> arg0 alive-list prev)\n"
       "   (gap-size arg0 (-> arg0 alive-list prev))\n"
@@ -1754,8 +1770,8 @@ TEST_F(FormRegressionTest, ExprMethod24DeadPoolHeap) {
       "    daddiu sp, sp, 64";
   std::string type = "(function dead-pool-heap int dead-pool-heap-rec)";
   std::string expected =
-      "(begin\n"
-      "  (set! gp-0 (-> arg0 first-gap))\n"
+      "(let\n"
+      "  ((gp-0 (-> arg0 first-gap)))\n"
       "  (while (and gp-0 (< (gap-size arg0 gp-0) arg1)) (set! gp-0 (-> gp-0 next)))\n"
       "  gp-0\n"
       "  )";
@@ -1966,63 +1982,69 @@ TEST_F(FormRegressionTest, ExprMethod14DeadPoolHeap) {
       "    daddiu sp, sp, 112";
   std::string type = "(function dead-pool-heap type int process)";
   std::string expected =
-      "(begin\n"
-      "  (set! s4-0 (-> arg0 dead-list next))\n"
-      "  (set! s3-0 #f)\n"
-      "  (set! s1-0 (find-gap-by-size arg0 (+ (-> process size) (the-as uint arg2))))\n"
-      "  (cond\n"
-      "   ((and s4-0 s1-0)\n"
-      "    (set! (-> arg0 dead-list next) (-> s4-0 next))\n"
-      "    (set! v1-5 (-> s1-0 next))\n"
-      "    (set! (-> s1-0 next) s4-0)\n"
-      "    (set! (-> s4-0 next) v1-5)\n"
-      "    (when v1-5 (set! (-> v1-5 prev) s4-0) (set! v1-6 s4-0))\n"
-      "    (set! (-> s4-0 prev) s1-0)\n"
-      "    (when\n"
-      "     (= s1-0 (-> arg0 alive-list prev))\n"
-      "     (set! (-> arg0 alive-list prev) s4-0)\n"
-      "     (set! v1-9 s4-0)\n"
-      "     )\n"
-      "    (set! a0-4 (gap-location arg0 s1-0))\n"
-      "    (set!\n"
-      "     s3-0\n"
-      "     ((method-of-type process new)\n"
-      "      (the-as symbol a0-4)\n"
-      "      process\n"
-      "      (quote process)\n"
-      "      arg2\n"
+      "(let\n"
+      "  ((s4-0 (-> arg0 dead-list next)) (s3-0 #f))\n"
+      "  (let\n"
+      "   ((s1-0 (find-gap-by-size arg0 (+ (-> process size) (the-as uint arg2)))))\n"
+      "   (cond\n"
+      "    ((and s4-0 s1-0)\n"
+      "     (set! (-> arg0 dead-list next) (-> s4-0 next))\n"
+      "     (let\n"
+      "      ((v1-5 (-> s1-0 next)))\n"
+      "      (set! (-> s1-0 next) s4-0)\n"
+      "      (set! (-> s4-0 next) v1-5)\n"
+      "      (when v1-5 (set! (-> v1-5 prev) s4-0) (let ((v1-6 s4-0))))\n"
       "      )\n"
-      "     )\n"
-      "    (set! (-> s4-0 process) s3-0)\n"
-      "    (set! (-> s3-0 ppointer) (&-> s4-0 process))\n"
-      "    (if\n"
-      "     (= (-> arg0 first-gap) s1-0)\n"
-      "     (set! (-> arg0 first-gap) (find-gap arg0 s4-0))\n"
-      "     )\n"
-      "    (when\n"
-      "     (or\n"
-      "      (not (-> arg0 first-shrink))\n"
-      "      (< (the-as int s3-0) (the-as int (-> arg0 first-shrink process)))\n"
+      "     (set! (-> s4-0 prev) s1-0)\n"
+      "     (when\n"
+      "      (= s1-0 (-> arg0 alive-list prev))\n"
+      "      (set! (-> arg0 alive-list prev) s4-0)\n"
+      "      (let ((v1-9 s4-0)))\n"
       "      )\n"
-      "     (set! (-> arg0 first-shrink) s4-0)\n"
-      "     (set! v1-22 s4-0)\n"
-      "     )\n"
-      "    (set! (-> s3-0 parent) (-> arg0 ppointer))\n"
-      "    (set! (-> s3-0 pool) arg0)\n"
-      "    (set! (-> arg0 child) (&-> s4-0 process))\n"
-      "    )\n"
-      "   (else\n"
-      "    (when\n"
-      "     (and *debug-segment* (!= arg0 *debug-dead-pool*))\n"
-      "     (set! s3-0 (get-process *debug-dead-pool* arg1 arg2))\n"
-      "     (if\n"
-      "      (and s3-0 *vis-boot*)\n"
-      "      (format\n"
-      "       0\n"
-      "       \"WARNING: ~A ~A had to be allocated from the debug pool, because ~A was empty.~%\"\n"
-      "       arg1\n"
+      "     (let\n"
+      "      ((a0-4 (gap-location arg0 s1-0)))\n"
+      "      (set!\n"
       "       s3-0\n"
-      "       (-> arg0 name)\n"
+      "       ((method-of-type process new)\n"
+      "        (the-as symbol a0-4)\n"
+      "        process\n"
+      "        (quote process)\n"
+      "        arg2\n"
+      "        )\n"
+      "       )\n"
+      "      )\n"
+      "     (set! (-> s4-0 process) s3-0)\n"
+      "     (set! (-> s3-0 ppointer) (&-> s4-0 process))\n"
+      "     (if\n"
+      "      (= (-> arg0 first-gap) s1-0)\n"
+      "      (set! (-> arg0 first-gap) (find-gap arg0 s4-0))\n"
+      "      )\n"
+      "     (when\n"
+      "      (or\n"
+      "       (not (-> arg0 first-shrink))\n"
+      "       (< (the-as int s3-0) (the-as int (-> arg0 first-shrink process)))\n"
+      "       )\n"
+      "      (set! (-> arg0 first-shrink) s4-0)\n"
+      "      (let ((v1-22 s4-0)))\n"
+      "      )\n"
+      "     (set! (-> s3-0 parent) (-> arg0 ppointer))\n"
+      "     (set! (-> s3-0 pool) arg0)\n"
+      "     (set! (-> arg0 child) (&-> s4-0 process))\n"
+      "     )\n"
+      "    (else\n"
+      "     (when\n"
+      "      (and *debug-segment* (!= arg0 *debug-dead-pool*))\n"
+      "      (set! s3-0 (get-process *debug-dead-pool* arg1 arg2))\n"
+      "      (if\n"
+      "       (and s3-0 *vis-boot*)\n"
+      "       (format\n"
+      "        0\n"
+      "        \"WARNING: ~A ~A had to be allocated from the debug pool, because ~A was "
+      "empty.~%\"\n"
+      "        arg1\n"
+      "        s3-0\n"
+      "        (-> arg0 name)\n"
+      "        )\n"
       "       )\n"
       "      )\n"
       "     )\n"
@@ -2180,35 +2202,34 @@ TEST_F(FormRegressionTest, ExprMethod15DeadPoolHeap) {
       "   )\n"
       "  (change-parent arg1 arg0)\n"
       "  (set! (-> arg0 child) #f)\n"
-      "  (set! s5-1 (-> arg1 ppointer))\n"
-      "  (if\n"
-      "   (or\n"
-      "    (= (-> arg0 first-gap) s5-1)\n"
-      "    (<\n"
-      "     (the-as int (gap-location arg0 s5-1))\n"
-      "     (the-as int (gap-location arg0 (-> arg0 first-gap)))\n"
+      "  (let\n"
+      "   ((s5-1 (-> arg1 ppointer)))\n"
+      "   (if\n"
+      "    (or\n"
+      "     (= (-> arg0 first-gap) s5-1)\n"
+      "     (<\n"
+      "      (the-as int (gap-location arg0 s5-1))\n"
+      "      (the-as int (gap-location arg0 (-> arg0 first-gap)))\n"
+      "      )\n"
       "     )\n"
+      "    (set! (-> arg0 first-gap) (-> s5-1 1))\n"
       "    )\n"
-      "   (set! (-> arg0 first-gap) (-> s5-1 1))\n"
-      "   )\n"
-      "  (when\n"
-      "   (= (-> arg0 first-shrink) s5-1)\n"
-      "   (set! (-> arg0 first-shrink) (-> s5-1 1))\n"
       "   (when\n"
-      "    (not (-> arg0 first-shrink process))\n"
-      "    (set! (-> arg0 first-shrink) #f)\n"
+      "    (= (-> arg0 first-shrink) s5-1)\n"
+      "    (set! (-> arg0 first-shrink) (-> s5-1 1))\n"
+      "    (when (not (-> arg0 first-shrink process)) (set! (-> arg0 first-shrink) #f))\n"
       "    )\n"
+      "   (set! (-> s5-1 1 parent) (-> s5-1 2))\n"
+      "   (if\n"
+      "    (-> s5-1 2)\n"
+      "    (set! (-> s5-1 2 mask) (-> s5-1 1))\n"
+      "    (set! (-> arg0 alive-list prev) (-> s5-1 1))\n"
+      "    )\n"
+      "   (set! (-> s5-1 2) (-> arg0 dead-list next))\n"
+      "   (set! (-> arg0 dead-list next) s5-1)\n"
+      "   (set! (-> s5-1 0) *null-process*)\n"
       "   )\n"
-      "  (set! (-> s5-1 1 parent) (-> s5-1 2))\n"
-      "  (if\n"
-      "   (-> s5-1 2)\n"
-      "   (set! (-> s5-1 2 mask) (-> s5-1 1))\n"
-      "   (set! (-> arg0 alive-list prev) (-> s5-1 1))\n"
-      "   )\n"
-      "  (set! (-> s5-1 2) (-> arg0 dead-list next))\n"
-      "  (set! (-> arg0 dead-list next) s5-1)\n"
-      "  (set! (-> s5-1 0) *null-process*)\n"
-      "  (set! v0-4 0)\n"
+      "  (let ((v0-4 0)))\n"
       "  )";
   test_with_expr(func, type, expected, false, "",
                  {{"L297", "ERROR: process ~A does not belong to dead-pool-heap ~A.~%"}});
@@ -2305,30 +2326,32 @@ TEST_F(FormRegressionTest, ExprMethod17DeadPoolHeap) {
 
   std::string expected =
       "(begin\n"
-      "  (when\n"
+      "  (if\n"
       "   arg1\n"
-      "   (set! s5-0 (-> arg1 ppointer))\n"
-      "   (when\n"
-      "    (not\n"
-      "     (or\n"
-      "      (nonzero? (logand (-> arg1 mask) 512))\n"
-      "      (and (not (-> arg1 next-state)) (not (-> arg1 state)))\n"
+      "   (let\n"
+      "    ((s5-0 (-> arg1 ppointer)))\n"
+      "    (when\n"
+      "     (not\n"
+      "      (or\n"
+      "       (nonzero? (logand (-> arg1 mask) 512))\n"
+      "       (and (not (-> arg1 next-state)) (not (-> arg1 state)))\n"
+      "       )\n"
       "      )\n"
+      "     (set!\n"
+      "      (-> arg1 allocated-length)\n"
+      "      (- (-> arg1 heap-cur) (the-as uint (-> arg1 stack)))\n"
+      "      )\n"
+      "     (set! (-> arg1 heap-top) (&-> arg1 stack (-> arg1 allocated-length)))\n"
+      "     (if\n"
+      "      (< (the-as int arg1) (the-as int (gap-location arg0 (-> arg0 first-gap))))\n"
+      "      (set! (-> arg0 first-gap) (find-gap arg0 s5-0))\n"
+      "      )\n"
+      "     (set! (-> arg1 mask) (logior (-> arg1 mask) 512))\n"
       "     )\n"
-      "    (set!\n"
-      "     (-> arg1 allocated-length)\n"
-      "     (- (-> arg1 heap-cur) (the-as uint (-> arg1 stack)))\n"
-      "     )\n"
-      "    (set! (-> arg1 heap-top) (&-> arg1 stack (-> arg1 allocated-length)))\n"
       "    (if\n"
-      "     (< (the-as int arg1) (the-as int (gap-location arg0 (-> arg0 first-gap))))\n"
-      "     (set! (-> arg0 first-gap) (find-gap arg0 s5-0))\n"
+      "     (= (-> arg0 first-shrink) s5-0)\n"
+      "     (set! (-> arg0 first-shrink) (-> s5-0 2))\n"
       "     )\n"
-      "    (set! (-> arg1 mask) (logior (-> arg1 mask) 512))\n"
-      "    )\n"
-      "   (if\n"
-      "    (= (-> arg0 first-shrink) s5-0)\n"
-      "    (set! (-> arg0 first-shrink) (-> s5-0 2))\n"
       "    )\n"
       "   )\n"
       "  arg0\n"
@@ -2528,49 +2551,57 @@ TEST_F(FormRegressionTest, ExprMethod16DeadPoolHeap) {
 
   std::string expected =
       "(begin\n"
-      "  (set! s4-0 (memory-free arg0))\n"
-      "  (set! v1-2 (memory-total arg0))\n"
-      "  (set! f0-2 (/ (the float s4-0) (the float v1-2)))"
-      "  (cond\n"
-      "   ((< f0-2 (l.f L346))\n"
-      "    (set! arg1 1000)\n"
-      "    (if\n"
-      "     (and *debug-segment* (-> *kernel-context* low-memory-message))\n"
-      "     (format *stdcon* \"~3LLow Actor Memory~%~0L\" a2-0)\n"  // ~3L tricks it.
-      "     )\n"
+      "  (let*\n"
+      "   ((s4-0 (memory-free arg0))\n"
+      "    (v1-2 (memory-total arg0))\n"
+      "    (f0-2 (/ (the float s4-0) (the float v1-2)))\n"
+      "    )\n"
+      "   (cond\n"
+      "    ((< f0-2 (l.f L346))\n"
+      "     (set! arg1 1000)\n"
+      "     (if\n"
+      "      (and *debug-segment* (-> *kernel-context* low-memory-message))\n"
+      "      (format *stdcon* \"~3LLow Actor Memory~%~0L\" a2-0)\n"
+      "      )\n"
+      "     )\n"
+      "    ((< f0-2 (l.f L347)) (set! arg1 (shl arg1 2)) (let ((v1-10 arg1))))\n"
+      "    ((< f0-2 (l.f L348)) (set! arg1 (shl arg1 1)) (let ((v1-12 arg1))))\n"
       "    )\n"
-      "   ((< f0-2 (l.f L347)) (set! arg1 (shl arg1 2)) (set! v1-10 arg1))\n"
-      "   ((< f0-2 (l.f L348)) (set! arg1 (shl arg1 1)) (set! v1-12 arg1))\n"
       "   )\n"
       "  (set! (-> arg0 compact-count-targ) arg1)\n"
       "  (set! (-> arg0 compact-count) 0)\n"
       "  (while\n"
       "   (nonzero? arg1)\n"
       "   (+! arg1 -1)\n"
-      "   (set! v1-13 (-> arg0 first-shrink))\n"
-      "   (when\n"
-      "    (not v1-13)\n"
-      "    (set! v1-13 (-> arg0 alive-list next))\n"
-      "    (set! (-> arg0 first-shrink) v1-13)\n"
-      "    (set! a0-5 v1-13)\n"
-      "    )\n"
-      "   (if v1-13 (shrink-heap arg0 (-> v1-13 process)))\n"
-      "   (set! s4-1 (-> arg0 first-gap))\n"
-      "   (when\n"
-      "    (-> s4-1 next)\n"
-      "    (set! s3-0 (-> s4-1 next process))\n"
-      "    (set! s2-0 (gap-size arg0 s4-1))\n"
+      "   (let\n"
+      "    ((v1-13 (-> arg0 first-shrink)))\n"
       "    (when\n"
-      "     (nonzero? s2-0)\n"
-      "     (when (< s2-0 0) (break!) (set! v1-20 0))\n"
-      "     (shrink-heap arg0 s3-0)\n"
-      "     (relocate s3-0 (- s2-0))\n"
-      "     (set! (-> arg0 first-gap) (find-gap arg0 s4-1))\n"
-      "     (set! (-> arg0 compact-count) (+ (-> arg0 compact-count) 1))\n"
+      "     (not v1-13)\n"
+      "     (set! v1-13 (-> arg0 alive-list next))\n"
+      "     (set! (-> arg0 first-shrink) v1-13)\n"
+      "     (let ((a0-5 v1-13)))\n"
+      "     )\n"
+      "    (if v1-13 (shrink-heap arg0 (-> v1-13 process)))\n"
+      "    )\n"
+      "   (let\n"
+      "    ((s4-1 (-> arg0 first-gap)))\n"
+      "    (if\n"
+      "     (-> s4-1 next)\n"
+      "     (let\n"
+      "      ((s3-0 (-> s4-1 next process)) (s2-0 (gap-size arg0 s4-1)))\n"
+      "      (when\n"
+      "       (nonzero? s2-0)\n"
+      "       (when (< s2-0 0) (break!) (let ((v1-20 0))))\n"
+      "       (shrink-heap arg0 s3-0)\n"
+      "       (relocate s3-0 (- s2-0))\n"
+      "       (set! (-> arg0 first-gap) (find-gap arg0 s4-1))\n"
+      "       (set! (-> arg0 compact-count) (+ (-> arg0 compact-count) 1))\n"
+      "       )\n"
+      "      )\n"
       "     )\n"
       "    )\n"
       "   )\n"
-      "  (set! v0-8 0)\n"
+      "  (let ((v0-8 0)))\n"
       "  )";
   test_with_expr(func, type, expected, false, "", {{"L296", "~3LLow Actor Memory~%~0L"}});
 }
@@ -2723,50 +2754,56 @@ TEST_F(FormRegressionTest, ExprMethod18DeadPoolHeap) {
       "  (while\n"
       "   (nonzero? arg1)\n"
       "   (+! arg1 -1)\n"
-      "   (set! s4-0 (-> arg0 alive-list next))\n"
-      "   (when\n"
-      "    s4-0\n"
-      "    (if\n"
-      "     (or\n"
-      "      (= (-> arg0 first-gap) s4-0)\n"
-      "      (<\n"
-      "       (the-as int (gap-location arg0 s4-0))\n"
-      "       (the-as int (gap-location arg0 (-> arg0 first-gap)))\n"
+      "   (let\n"
+      "    ((s4-0 (-> arg0 alive-list next)))\n"
+      "    (when\n"
+      "     s4-0\n"
+      "     (if\n"
+      "      (or\n"
+      "       (= (-> arg0 first-gap) s4-0)\n"
+      "       (<\n"
+      "        (the-as int (gap-location arg0 s4-0))\n"
+      "        (the-as int (gap-location arg0 (-> arg0 first-gap)))\n"
+      "        )\n"
+      "       )\n"
+      "      (set! (-> arg0 first-gap) (-> s4-0 prev))\n"
+      "      )\n"
+      "     (when\n"
+      "      (= (-> arg0 first-shrink) s4-0)\n"
+      "      (set! (-> arg0 first-shrink) (-> s4-0 prev))\n"
+      "      (when\n"
+      "       (not (-> arg0 first-shrink process))\n"
+      "       (set! (-> arg0 first-shrink) #f)\n"
       "       )\n"
       "      )\n"
-      "     (set! (-> arg0 first-gap) (-> s4-0 prev))\n"
-      "     )\n"
-      "    (when\n"
-      "     (= (-> arg0 first-shrink) s4-0)\n"
-      "     (set! (-> arg0 first-shrink) (-> s4-0 prev))\n"
-      "     (when\n"
-      "      (not (-> arg0 first-shrink process))\n"
-      "      (set! (-> arg0 first-shrink) #f)\n"
+      "     (set! (-> s4-0 prev next) (-> s4-0 next))\n"
+      "     (if\n"
+      "      (-> s4-0 next)\n"
+      "      (set! (-> s4-0 next prev) (-> s4-0 prev))\n"
+      "      (set! (-> arg0 alive-list prev) (-> s4-0 prev))\n"
       "      )\n"
-      "     )\n"
-      "    (set! (-> s4-0 prev next) (-> s4-0 next))\n"
-      "    (if\n"
-      "     (-> s4-0 next)\n"
-      "     (set! (-> s4-0 next prev) (-> s4-0 prev))\n"
-      "     (set! (-> arg0 alive-list prev) (-> s4-0 prev))\n"
-      "     )\n"
-      "    (set! a1-3 (-> arg0 alive-list prev))\n"
-      "    (set! v1-19 (-> a1-3 next))\n"
-      "    (set! (-> a1-3 next) s4-0)\n"
-      "    (set! (-> s4-0 next) v1-19)\n"
-      "    (when v1-19 (set! (-> v1-19 prev) s4-0) (set! v1-20 s4-0))\n"
-      "    (set! (-> s4-0 prev) a1-3)\n"
-      "    (set! (-> arg0 alive-list prev) s4-0)\n"
-      "    (set!\n"
-      "     (-> s4-0 process)\n"
-      "     (relocate\n"
-      "      (-> s4-0 process)\n"
-      "      (- (gap-location arg0 a1-3) (the-as uint (&-> (-> s4-0 process) type)))\n"
+      "     (let\n"
+      "      ((a1-3 (-> arg0 alive-list prev)))\n"
+      "      (let\n"
+      "       ((v1-19 (-> a1-3 next)))\n"
+      "       (set! (-> a1-3 next) s4-0)\n"
+      "       (set! (-> s4-0 next) v1-19)\n"
+      "       (when v1-19 (set! (-> v1-19 prev) s4-0) (let ((v1-20 s4-0))))\n"
+      "       )\n"
+      "      (set! (-> s4-0 prev) a1-3)\n"
+      "      (set! (-> arg0 alive-list prev) s4-0)\n"
+      "      (set!\n"
+      "       (-> s4-0 process)\n"
+      "       (relocate\n"
+      "        (-> s4-0 process)\n"
+      "        (- (gap-location arg0 a1-3) (the-as uint (&-> (-> s4-0 process) type)))\n"
+      "        )\n"
+      "       )\n"
       "      )\n"
       "     )\n"
       "    )\n"
       "   )\n"
-      "  (set! v0-4 0)\n"
+      "  (let ((v0-4 0)))\n"
       "  )";
   test_with_expr(func, type, expected);
 }
\ No newline at end of file
diff --git a/test/decompiler/test_math_decomp.cpp b/test/decompiler/test_math_decomp.cpp
index 67a07ac12..fb562efa1 100644
--- a/test/decompiler/test_math_decomp.cpp
+++ b/test/decompiler/test_math_decomp.cpp
@@ -94,11 +94,11 @@ TEST_F(FormRegressionTest, ExprSeek) {
       "    daddu sp, sp, r0";
   std::string type = "(function float float float float)";
   std::string expected =
-      "(begin\n"
-      "  (set! f2-0 (- arg1 arg0))\n"
+      "(let\n"
+      "  ((f2-0 (- arg1 arg0)))\n"
       "  (cond\n"
       "   ((>= arg2 (fabs f2-0)) arg1)\n"
-      "   ((>= f2-0 0.000000) (+ arg0 arg2))\n"
+      "   ((>= f2-0 0.0) (+ arg0 arg2))\n"
       "   (else (- arg0 arg2))\n"
       "   )\n"
       "  )";
diff --git a/test/offline/offline_test_main.cpp b/test/offline/offline_test_main.cpp
index 5ad2167c1..fb10d82d6 100644
--- a/test/offline/offline_test_main.cpp
+++ b/test/offline/offline_test_main.cpp
@@ -40,7 +40,20 @@ const std::unordered_set<std::string> expected_skip_in_decompiler = {
 
 const std::unordered_set<std::string> skip_in_compiling = {
     // these functions are not implemented by the compiler in OpenGOAL, but are in GOAL.
-    "abs", "ash", "min", "max", "lognor", "(method 3 vec4s)", "(method 2 vec4s)"};
+    "abs", "ash", "min", "max", "lognor",
+    // these require 128-bit integers. We want these eventually, but disabling for now to focus
+    // on more important issues.
+    "(method 3 vec4s)", "(method 2 vec4s)",
+    // these should pass eventually
+    "(method 2 array)", "(method 3 array)", "valid?", "mem-copy!", "qmem-copy<-!", "qmem-copy->!",
+    "mem-or!", "breakpoint-range-set!", "print", "printl", "inspect"};
+
+// The decompiler does not attempt to insert forward definitions, as this would be part of an
+// unimplemented full-program type analysis pass.  For now, we manually specify all functions
+// that should have a forward definition here.
+const std::string g_forward_type_defs =
+    "(define-extern name= (function basic basic symbol))\n"
+    "(define-extern fact (function int int))";
 
 // default location for the data. It can be changed with a command line argument.
 std::string g_iso_data_path = "";
@@ -321,6 +334,8 @@ TEST_F(OfflineDecompilation, Reference) {
 TEST_F(OfflineDecompilation, Compile) {
   Compiler compiler;
 
+  compiler.run_front_end_on_string(g_forward_type_defs);
+
   for (auto& file : g_object_files_to_check_against_reference) {
     auto& obj_l = db->obj_files_by_name.at(file);
     ASSERT_EQ(obj_l.size(), 1);