diff --git a/Cargo.lock b/Cargo.lock
index eecbb0c..8f82233 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -342,6 +342,7 @@ dependencies = [
  "smallvec",
  "smartstring",
  "tracing",
+ "typed-arena",
 ]
 
 [[package]]
@@ -946,6 +947,12 @@ dependencies = [
  "tracing-log",
 ]
 
+[[package]]
+name = "typed-arena"
+version = "2.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6af6ae20167a9ece4bcb41af5b80f8a1f1df981f6391189ce00fd257af04126a"
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.13"
diff --git a/dust-lang/Cargo.toml b/dust-lang/Cargo.toml
index 28c86ac..1de72f1 100644
--- a/dust-lang/Cargo.toml
+++ b/dust-lang/Cargo.toml
@@ -22,6 +22,7 @@ smartstring = { version = "1.0.1", features = [
     "serde",
 ], default-features = false }
 tracing = "0.1.41"
+typed-arena = "2.0.2"
 
 [dev-dependencies]
 criterion = { version = "0.3.4", features = ["html_reports"] }
diff --git a/dust-lang/src/chunk/mod.rs b/dust-lang/src/chunk/mod.rs
index 277edbf..05eb799 100644
--- a/dust-lang/src/chunk/mod.rs
+++ b/dust-lang/src/chunk/mod.rs
@@ -42,7 +42,7 @@ pub struct Chunk {
     pub(crate) locals: SmallVec<[Local; 8]>,
     pub(crate) prototypes: Vec<Chunk>,
 
-    pub(crate) stack_size: usize,
+    pub(crate) register_count: usize,
     pub(crate) prototype_index: u8,
 }
 
@@ -65,7 +65,7 @@ impl Chunk {
             constants: constants.into(),
             locals: locals.into(),
             prototypes,
-            stack_size: 0,
+            register_count: 0,
             prototype_index: 0,
         }
     }
diff --git a/dust-lang/src/compiler/mod.rs b/dust-lang/src/compiler/mod.rs
index 0fbbb77..2e19050 100644
--- a/dust-lang/src/compiler/mod.rs
+++ b/dust-lang/src/compiler/mod.rs
@@ -214,7 +214,7 @@ impl<'src> Compiler<'src> {
             constants: self.constants,
             locals,
             prototypes: self.prototypes,
-            stack_size: self.stack_size,
+            register_count: self.stack_size,
             prototype_index: self.prototype_index,
         }
     }
@@ -1000,9 +1000,9 @@ impl<'src> Compiler<'src> {
             return self.parse_call_native(native_function);
         } else if self.function_name.as_deref() == Some(identifier) {
             let destination = self.next_register();
-            let load_function = Instruction::load_function(destination, self.prototype_index);
+            let load_self = Instruction::load_self(destination);
 
-            self.emit_instruction(load_function, Type::SelfFunction, start_position);
+            self.emit_instruction(load_self, Type::SelfFunction, start_position);
 
             return Ok(());
         } else {
@@ -1700,6 +1700,7 @@ impl<'src> Compiler<'src> {
                 });
             }
         };
+        let is_recursive = last_instruction_type == &Type::SelfFunction;
 
         let mut argument_count = 0;
 
@@ -1727,7 +1728,7 @@ impl<'src> Compiler<'src> {
 
         let end = self.current_position.1;
         let destination = self.next_register();
-        let call = Instruction::call(destination, function_register, argument_count);
+        let call = Instruction::call(destination, function_register, argument_count, is_recursive);
 
         self.emit_instruction(call, function_return_type, Span(start, end));
 
diff --git a/dust-lang/src/instruction/call.rs b/dust-lang/src/instruction/call.rs
index 1a8213e..dff0679 100644
--- a/dust-lang/src/instruction/call.rs
+++ b/dust-lang/src/instruction/call.rs
@@ -4,6 +4,7 @@ pub struct Call {
     pub destination: u8,
     pub function_register: u8,
     pub argument_count: u8,
+    pub is_recursive: bool,
 }
 
 impl From<Instruction> for Call {
@@ -11,11 +12,13 @@ impl From<Instruction> for Call {
         let destination = instruction.a_field();
         let function_register = instruction.b_field();
         let argument_count = instruction.c_field();
+        let is_recursive = instruction.d_field();
 
         Call {
             destination,
             function_register,
             argument_count,
+            is_recursive,
         }
     }
 }
@@ -25,7 +28,8 @@ impl From<Call> for Instruction {
         let a = call.destination;
         let b = call.function_register;
         let c = call.argument_count;
+        let d = call.is_recursive;
 
-        Instruction::new(Operation::CALL, a, b, c, false, false, false)
+        Instruction::new(Operation::CALL, a, b, c, false, false, d)
     }
 }
diff --git a/dust-lang/src/instruction/mod.rs b/dust-lang/src/instruction/mod.rs
index 73aa3a1..e0a32e7 100644
--- a/dust-lang/src/instruction/mod.rs
+++ b/dust-lang/src/instruction/mod.rs
@@ -375,11 +375,17 @@ impl Instruction {
         })
     }
 
-    pub fn call(destination: u8, function_register: u8, argument_count: u8) -> Instruction {
+    pub fn call(
+        destination: u8,
+        function_register: u8,
+        argument_count: u8,
+        is_recursive: bool,
+    ) -> Instruction {
         Instruction::from(Call {
             destination,
             function_register,
             argument_count,
+            is_recursive,
         })
     }
 
@@ -691,6 +697,7 @@ impl Instruction {
                     destination,
                     function_register,
                     argument_count,
+                    ..
                 } = Call::from(*self);
                 let arguments_start = destination.saturating_sub(argument_count);
 
diff --git a/dust-lang/src/native_function/assertion.rs b/dust-lang/src/native_function/assertion.rs
index 2edc9be..c0d4b45 100644
--- a/dust-lang/src/native_function/assertion.rs
+++ b/dust-lang/src/native_function/assertion.rs
@@ -14,7 +14,7 @@ pub fn panic(
     let mut message = format!("Dust panic at {position}!");
 
     for register_index in argument_range {
-        let value = record.open_register(register_index);
+        let value = record.open_register_unchecked(register_index);
 
         if let Some(string) = value.as_string() {
             message.push_str(string);
diff --git a/dust-lang/src/native_function/string.rs b/dust-lang/src/native_function/string.rs
index a4db8dd..2d48ce7 100644
--- a/dust-lang/src/native_function/string.rs
+++ b/dust-lang/src/native_function/string.rs
@@ -10,7 +10,7 @@ pub fn to_string(
     destination: Option<u8>,
     argument_range: Range<u8>,
 ) -> Result<ThreadSignal, NativeFunctionError> {
-    let argument_value = record.open_register(argument_range.start);
+    let argument_value = record.open_register_unchecked(argument_range.start);
     let argument_string = argument_value.display(record);
     let destination = destination.unwrap();
     let register = Register::Value(Value::Concrete(ConcreteValue::string(argument_string)));
diff --git a/dust-lang/src/vm/error.rs b/dust-lang/src/vm/error.rs
index a437edf..1c71da4 100644
--- a/dust-lang/src/vm/error.rs
+++ b/dust-lang/src/vm/error.rs
@@ -6,7 +6,7 @@ use super::{stack::Stack, FunctionCall};
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum VmError {
-    CallStackUnderflow,
+    StackUnderflow,
     ExpectedFunction {
         value: Value,
     },
@@ -22,7 +22,7 @@ pub enum VmError {
 impl Display for VmError {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self {
-            Self::CallStackUnderflow => {
+            Self::StackUnderflow => {
                 write!(f, "Call stack underflow")
             }
             Self::ExpectedFunction { value } => {
diff --git a/dust-lang/src/vm/mod.rs b/dust-lang/src/vm/mod.rs
index 147a825..dc52e98 100644
--- a/dust-lang/src/vm/mod.rs
+++ b/dust-lang/src/vm/mod.rs
@@ -13,7 +13,7 @@ use std::{
 
 pub use error::VmError;
 pub use record::Record;
-pub use run_action::RunAction;
+pub use run_action::RecordAction;
 pub use stack::{FunctionCall, Stack};
 pub use thread::{Thread, ThreadSignal};
 use tracing::{span, Level};
diff --git a/dust-lang/src/vm/record.rs b/dust-lang/src/vm/record.rs
index 1920fca..8c709a7 100644
--- a/dust-lang/src/vm/record.rs
+++ b/dust-lang/src/vm/record.rs
@@ -10,7 +10,7 @@ use super::{Pointer, Register};
 pub struct Record<'a> {
     pub ip: usize,
     pub chunk: &'a Chunk,
-    stack: Vec<Register>,
+    registers: Vec<Register>,
 }
 
 impl<'a> Record<'a> {
@@ -18,7 +18,7 @@ impl<'a> Record<'a> {
     pub fn new(chunk: &'a Chunk) -> Self {
         Self {
             ip: 0,
-            stack: vec![Register::Empty; chunk.stack_size],
+            registers: vec![Register::Empty; chunk.register_count],
             chunk,
         }
     }
@@ -28,7 +28,7 @@ impl<'a> Record<'a> {
     }
 
     pub fn stack_size(&self) -> usize {
-        self.stack.len()
+        self.registers.len()
     }
 
     pub fn current_position(&self) -> Span {
@@ -43,59 +43,46 @@ impl<'a> Record<'a> {
         trace!("Follow pointer {pointer}");
 
         match pointer {
-            Pointer::Stack(register_index) => self.open_register(register_index),
+            Pointer::Stack(register_index) => self.open_register_unchecked(register_index),
             Pointer::Constant(constant_index) => self.get_constant(constant_index),
         }
     }
 
-    pub fn get_register(&self, register_index: u8) -> &Register {
+    pub fn get_register_unchecked(&self, register_index: u8) -> &Register {
         trace!("Get register R{register_index}");
 
         let register_index = register_index as usize;
 
-        assert!(
-            register_index < self.stack.len(),
-            "VM Error: Register index out of bounds"
-        );
-
-        &self.stack[register_index]
+        if cfg!(debug_assertions) {
+            &self.registers[register_index]
+        } else {
+            unsafe { self.registers.get_unchecked(register_index) }
+        }
     }
 
     pub fn set_register(&mut self, to_register: u8, register: Register) {
         let to_register = to_register as usize;
 
-        assert!(
-            to_register < self.stack.len(),
-            "VM Error: Register index out of bounds"
-        );
-
-        self.stack[to_register] = register;
+        self.registers[to_register] = register;
     }
 
-    pub fn reserve_registers(&mut self, count: usize) {
-        for _ in 0..count {
-            self.stack.push(Register::Empty);
-        }
-    }
-
-    pub fn open_register(&self, register_index: u8) -> &Value {
+    pub fn open_register_unchecked(&self, register_index: u8) -> &Value {
         let register_index = register_index as usize;
 
-        assert!(
-            register_index < self.stack.len(),
-            "VM Error: Register index out of bounds"
-        );
-
-        let register = &self.stack[register_index];
+        let register = if cfg!(debug_assertions) {
+            &self.registers[register_index]
+        } else {
+            unsafe { self.registers.get_unchecked(register_index) }
+        };
 
         match register {
             Register::Value(value) => {
-                trace!("Register R{register_index} openned to value {value}");
+                trace!("Register R{register_index} opened to value {value}");
 
                 value
             }
             Register::Pointer(pointer) => {
-                trace!("Open register R{register_index} openned to pointer {pointer}");
+                trace!("Open register R{register_index} opened to pointer {pointer}");
 
                 self.follow_pointer(*pointer)
             }
@@ -109,11 +96,11 @@ impl<'a> Record<'a> {
         let register_index = register_index as usize;
 
         assert!(
-            register_index < self.stack.len(),
+            register_index < self.registers.len(),
             "VM Error: Register index out of bounds"
         );
 
-        let register = &self.stack[register_index];
+        let register = &self.registers[register_index];
 
         match register {
             Register::Value(value) => {
@@ -130,24 +117,22 @@ impl<'a> Record<'a> {
         }
     }
 
-    pub fn empty_register_or_clone_constant(
-        &mut self,
-        register_index: u8,
-        new_register: Register,
-    ) -> Value {
+    pub fn empty_register_or_clone_constant(&mut self, register_index: u8) -> Value {
         let register_index = register_index as usize;
 
         assert!(
-            register_index < self.stack.len(),
+            register_index < self.registers.len(),
             "VM Error: Register index out of bounds"
         );
 
-        let old_register = replace(&mut self.stack[register_index], new_register);
+        let old_register = replace(&mut self.registers[register_index], Register::Empty);
 
         match old_register {
             Register::Value(value) => value,
             Register::Pointer(pointer) => match pointer {
-                Pointer::Stack(register_index) => self.open_register(register_index).clone(),
+                Pointer::Stack(register_index) => {
+                    self.empty_register_or_clone_constant(register_index)
+                }
                 Pointer::Constant(constant_index) => self.get_constant(constant_index).clone(),
             },
             Register::Empty => panic!("VM Error: Register {register_index} is empty"),
@@ -156,16 +141,18 @@ impl<'a> Record<'a> {
 
     pub fn clone_register_value_or_constant(&self, register_index: u8) -> Value {
         assert!(
-            (register_index as usize) < self.stack.len(),
+            (register_index as usize) < self.registers.len(),
             "VM Error: Register index out of bounds"
         );
 
-        let register = &self.stack[register_index as usize];
+        let register = &self.registers[register_index as usize];
 
         match register {
             Register::Value(value) => value.clone(),
             Register::Pointer(pointer) => match pointer {
-                Pointer::Stack(register_index) => self.open_register(*register_index).clone(),
+                Pointer::Stack(register_index) => {
+                    self.open_register_unchecked(*register_index).clone()
+                }
                 Pointer::Constant(constant_index) => self.get_constant(*constant_index).clone(),
             },
             Register::Empty => panic!("VM Error: Register {register_index} is empty"),
@@ -176,7 +163,7 @@ impl<'a> Record<'a> {
     pub fn get_argument(&self, argument: Argument) -> &Value {
         match argument {
             Argument::Constant(constant_index) => self.get_constant(constant_index),
-            Argument::Register(register_index) => self.open_register(register_index),
+            Argument::Register(register_index) => self.open_register_unchecked(register_index),
         }
     }
 
diff --git a/dust-lang/src/vm/run_action.rs b/dust-lang/src/vm/run_action.rs
index 3ea79a0..f520c23 100644
--- a/dust-lang/src/vm/run_action.rs
+++ b/dust-lang/src/vm/run_action.rs
@@ -6,27 +6,28 @@ use crate::{
         LoadConstant, LoadFunction, LoadList, LoadSelf, Modulo, Multiply, Negate, Not, Point,
         Return, SetLocal, Subtract, Test, TestSet,
     },
-    AbstractList, Argument, ConcreteValue, Instruction, Type, Value,
+    vm::FunctionCall,
+    AbstractList, Argument, ConcreteValue, DustString, Instruction, Type, Value,
 };
 
-use super::{thread::ThreadSignal, Pointer, Record, Register};
+use super::{thread::ThreadData, Pointer, Record, Register};
 
 #[derive(Clone, Copy, Debug, PartialEq)]
-pub struct RunAction {
+pub struct RecordAction {
     pub logic: RunnerLogic,
     pub instruction: Instruction,
 }
 
-impl From<Instruction> for RunAction {
+impl From<Instruction> for RecordAction {
     fn from(instruction: Instruction) -> Self {
         let operation = instruction.operation();
         let logic = RUNNER_LOGIC_TABLE[operation.0 as usize];
 
-        RunAction { logic, instruction }
+        RecordAction { logic, instruction }
     }
 }
 
-pub type RunnerLogic = fn(Instruction, &mut Record) -> ThreadSignal;
+pub type RunnerLogic = fn(Instruction, &mut ThreadData) -> Option<Value>;
 
 pub const RUNNER_LOGIC_TABLE: [RunnerLogic; 25] = [
     point,
@@ -56,9 +57,10 @@ pub const RUNNER_LOGIC_TABLE: [RunnerLogic; 25] = [
     r#return,
 ];
 
-pub fn point(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn point(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Point { from, to } = instruction.into();
-    let from_register = record.get_register(from);
+    let from_register = record.get_register_unchecked(from);
     let from_register_is_empty = matches!(from_register, Register::Empty);
 
     if !from_register_is_empty {
@@ -67,10 +69,13 @@ pub fn point(instruction: Instruction, record: &mut Record) -> ThreadSignal {
         record.set_register(from, register);
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn close(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn close(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Close { from, to } = instruction.into();
 
     assert!(from < to, "Runtime Error: Malformed instruction");
@@ -84,10 +89,13 @@ pub fn close(instruction: Instruction, record: &mut Record) -> ThreadSignal {
         record.set_register(register_index, Register::Empty);
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn load_boolean(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn load_boolean(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let LoadBoolean {
         destination,
         value,
@@ -102,10 +110,13 @@ pub fn load_boolean(instruction: Instruction, record: &mut Record) -> ThreadSign
         record.ip += 1;
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn load_constant(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn load_constant(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let LoadConstant {
         destination,
         constant_index,
@@ -121,10 +132,13 @@ pub fn load_constant(instruction: Instruction, record: &mut Record) -> ThreadSig
         record.ip += 1;
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn load_list(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn load_list(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let LoadList {
         destination,
         start_register,
@@ -133,7 +147,7 @@ pub fn load_list(instruction: Instruction, record: &mut Record) -> ThreadSignal
     let mut item_type = Type::Any;
 
     for register_index in start_register..destination {
-        match record.get_register(register_index) {
+        match record.get_register_unchecked(register_index) {
             Register::Empty => continue,
             Register::Value(value) => {
                 if item_type == Type::Any {
@@ -160,32 +174,43 @@ pub fn load_list(instruction: Instruction, record: &mut Record) -> ThreadSignal
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn load_function(instruction: Instruction, _: &mut Record) -> ThreadSignal {
+pub fn load_function(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let LoadFunction {
         destination,
         prototype_index,
     } = instruction.into();
+    let prototype_index = prototype_index as usize;
+    let function = record.chunk.prototypes[prototype_index].as_function();
+    let register = Register::Value(Value::Function(function));
 
-    ThreadSignal::LoadFunction {
-        destination,
-        prototype_index,
-    }
+    record.set_register(destination, register);
+
+    record.ip += 1;
+
+    None
 }
 
-pub fn load_self(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn load_self(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let LoadSelf { destination } = instruction.into();
     let function = record.as_function();
     let register = Register::Value(Value::Function(function));
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn get_local(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn get_local(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let GetLocal {
         destination,
         local_index,
@@ -195,10 +220,13 @@ pub fn get_local(instruction: Instruction, record: &mut Record) -> ThreadSignal
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn set_local(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn set_local(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let SetLocal {
         register_index,
         local_index,
@@ -208,10 +236,13 @@ pub fn set_local(instruction: Instruction, record: &mut Record) -> ThreadSignal
 
     record.set_register(local_register_index, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn add(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn add(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Add {
         destination,
         left,
@@ -224,10 +255,13 @@ pub fn add(instruction: Instruction, record: &mut Record) -> ThreadSignal {
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn subtract(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn subtract(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Subtract {
         destination,
         left,
@@ -240,10 +274,13 @@ pub fn subtract(instruction: Instruction, record: &mut Record) -> ThreadSignal {
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn multiply(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn multiply(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Multiply {
         destination,
         left,
@@ -264,10 +301,13 @@ pub fn multiply(instruction: Instruction, record: &mut Record) -> ThreadSignal {
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn divide(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn divide(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Divide {
         destination,
         left,
@@ -288,10 +328,13 @@ pub fn divide(instruction: Instruction, record: &mut Record) -> ThreadSignal {
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn modulo(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn modulo(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Modulo {
         destination,
         left,
@@ -312,15 +355,18 @@ pub fn modulo(instruction: Instruction, record: &mut Record) -> ThreadSignal {
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn test(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn test(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Test {
         operand_register,
         test_value,
     } = instruction.into();
-    let value = record.open_register(operand_register);
+    let value = record.open_register_unchecked(operand_register);
     let boolean = if let Value::Concrete(ConcreteValue::Boolean(boolean)) = value {
         *boolean
     } else {
@@ -331,10 +377,13 @@ pub fn test(instruction: Instruction, record: &mut Record) -> ThreadSignal {
         record.ip += 1;
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn test_set(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn test_set(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let TestSet {
         destination,
         argument,
@@ -359,10 +408,13 @@ pub fn test_set(instruction: Instruction, record: &mut Record) -> ThreadSignal {
         record.set_register(destination, register);
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn equal(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn equal(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Equal { value, left, right } = instruction.into();
     let left = record.get_argument(left);
     let right = record.get_argument(right);
@@ -372,10 +424,13 @@ pub fn equal(instruction: Instruction, record: &mut Record) -> ThreadSignal {
         record.ip += 1;
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn less(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn less(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Less { value, left, right } = instruction.into();
     let left = record.get_argument(left);
     let right = record.get_argument(right);
@@ -385,10 +440,13 @@ pub fn less(instruction: Instruction, record: &mut Record) -> ThreadSignal {
         record.ip += 1;
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn less_equal(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn less_equal(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let LessEqual { value, left, right } = instruction.into();
     let left = record.get_argument(left);
     let right = record.get_argument(right);
@@ -398,10 +456,13 @@ pub fn less_equal(instruction: Instruction, record: &mut Record) -> ThreadSignal
         record.ip += 1;
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn negate(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn negate(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Negate {
         destination,
         argument,
@@ -412,10 +473,13 @@ pub fn negate(instruction: Instruction, record: &mut Record) -> ThreadSignal {
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn not(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn not(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Not {
         destination,
         argument,
@@ -429,10 +493,13 @@ pub fn not(instruction: Instruction, record: &mut Record) -> ThreadSignal {
 
     record.set_register(destination, register);
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn jump(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn jump(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Jump {
         offset,
         is_positive,
@@ -445,24 +512,61 @@ pub fn jump(instruction: Instruction, record: &mut Record) -> ThreadSignal {
         record.ip -= offset + 1;
     }
 
-    ThreadSignal::Continue
+    record.ip += 1;
+
+    None
 }
 
-pub fn call(instruction: Instruction, _: &mut Record) -> ThreadSignal {
+pub fn call(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Call {
         destination: return_register,
         function_register,
         argument_count,
+        is_recursive,
     } = instruction.into();
 
-    ThreadSignal::Call {
-        function_register,
+    let function = record
+        .open_register_unchecked(function_register)
+        .as_function()
+        .unwrap();
+    let first_argument_register = return_register - argument_count;
+    let prototype = if is_recursive {
+        record.chunk
+    } else {
+        &record.chunk.prototypes[function.prototype_index as usize]
+    };
+    let mut next_record = Record::new(prototype);
+    let next_call = FunctionCall {
+        name: next_record.name().cloned(),
         return_register,
-        argument_count,
+        ip: record.ip,
+    };
+
+    for (argument_index, register_index) in (first_argument_register..return_register).enumerate() {
+        let argument = record.clone_register_value_or_constant(register_index);
+
+        trace!(
+            "Passing argument \"{argument}\" to {}",
+            function
+                .name
+                .clone()
+                .unwrap_or_else(|| DustString::from("anonymous"))
+        );
+
+        next_record.set_register(argument_index as u8, Register::Value(argument));
     }
+
+    record.ip += 1;
+
+    data.call_stack.push(next_call);
+    data.records.push(next_record);
+
+    None
 }
 
-pub fn call_native(instruction: Instruction, record: &mut Record) -> ThreadSignal {
+pub fn call_native(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let CallNative {
         destination,
         function,
@@ -473,19 +577,47 @@ pub fn call_native(instruction: Instruction, record: &mut Record) -> ThreadSigna
 
     function
         .call(record, Some(destination), argument_range)
-        .unwrap_or_else(|error| panic!("{error:?}"))
+        .unwrap_or_else(|error| panic!("{error:?}"));
+
+    record.ip += 1;
+
+    None
 }
 
-pub fn r#return(instruction: Instruction, _: &mut Record) -> ThreadSignal {
+pub fn r#return(instruction: Instruction, data: &mut ThreadData) -> Option<Value> {
+    let record = data.records.last_mut_unchecked();
     let Return {
         should_return_value,
         return_register,
     } = instruction.into();
 
-    ThreadSignal::Return {
-        should_return_value,
-        return_register,
+    trace!("Returning with call stack:\n{}", data.call_stack);
+
+    let return_value = if should_return_value {
+        Some(record.empty_register_or_clone_constant(return_register))
+    } else {
+        None
+    };
+
+    let current_call = data.call_stack.pop_unchecked();
+    let _current_record = data.records.pop_unchecked();
+    let destination = current_call.return_register;
+
+    if data.call_stack.is_empty() {
+        return if should_return_value {
+            return_value
+        } else {
+            None
+        };
     }
+
+    let outer_record = data.records.last_mut_unchecked();
+
+    if should_return_value {
+        outer_record.set_register(destination, Register::Value(return_value.unwrap()));
+    }
+
+    None
 }
 
 #[cfg(test)]
diff --git a/dust-lang/src/vm/stack.rs b/dust-lang/src/vm/stack.rs
index f04a12f..82e8562 100644
--- a/dust-lang/src/vm/stack.rs
+++ b/dust-lang/src/vm/stack.rs
@@ -33,6 +33,16 @@ impl<T> Stack<T> {
         self.items.len()
     }
 
+    pub fn get_unchecked(&self, index: usize) -> &T {
+        if cfg!(debug_assertions) {
+            assert!(index < self.len(), "{}", VmError::StackUnderflow);
+
+            &self.items[index]
+        } else {
+            unsafe { self.items.get_unchecked(index) }
+        }
+    }
+
     pub fn push(&mut self, item: T) {
         self.items.push(item);
     }
@@ -51,7 +61,7 @@ impl<T> Stack<T> {
 
     pub fn pop_unchecked(&mut self) -> T {
         if cfg!(debug_assertions) {
-            assert!(!self.is_empty(), "{}", VmError::CallStackUnderflow);
+            assert!(!self.is_empty(), "{}", VmError::StackUnderflow);
 
             self.items.pop().unwrap()
         } else {
@@ -61,7 +71,7 @@ impl<T> Stack<T> {
 
     pub fn last_unchecked(&self) -> &T {
         if cfg!(debug_assertions) {
-            assert!(!self.is_empty(), "{}", VmError::CallStackUnderflow);
+            assert!(!self.is_empty(), "{}", VmError::StackUnderflow);
 
             self.items.last().unwrap()
         } else {
@@ -71,7 +81,7 @@ impl<T> Stack<T> {
 
     pub fn last_mut_unchecked(&mut self) -> &mut T {
         if cfg!(debug_assertions) {
-            assert!(!self.is_empty(), "{}", VmError::CallStackUnderflow);
+            assert!(!self.is_empty(), "{}", VmError::StackUnderflow);
 
             self.items.last_mut().unwrap()
         } else {
@@ -100,9 +110,9 @@ impl<T> IndexMut<Range<usize>> for Stack<T> {
     }
 }
 
-impl Debug for Stack<FunctionCall> {
+impl<T: Debug> Debug for Stack<T> {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "{self}")
+        write!(f, "{:?}", self.items)
     }
 }
 
diff --git a/dust-lang/src/vm/thread.rs b/dust-lang/src/vm/thread.rs
index 287ceec..1dfad2e 100644
--- a/dust-lang/src/vm/thread.rs
+++ b/dust-lang/src/vm/thread.rs
@@ -2,12 +2,9 @@ use std::fmt::{self, Display, Formatter};
 
 use tracing::{info, trace};
 
-use crate::{
-    vm::{FunctionCall, Register},
-    Chunk, DustString, Value,
-};
+use crate::{vm::FunctionCall, Chunk, DustString, Value};
 
-use super::{record::Record, RunAction, Stack};
+use super::{record::Record, RecordAction, Stack};
 
 pub struct Thread {
     chunk: Chunk,
@@ -28,127 +25,43 @@ impl Thread {
         };
         let main_record = Record::new(&self.chunk);
 
-        call_stack.push(main_call);
-        records.push(main_record);
-
-        let mut active_record = records.last_mut_unchecked();
-
         info!(
             "Starting thread with {}",
-            active_record
-                .as_function()
+            self.chunk
                 .name
+                .clone()
                 .unwrap_or_else(|| DustString::from("anonymous"))
         );
 
+        call_stack.push(main_call);
+        records.push(main_record);
+
+        let mut thread_data = ThreadData {
+            call_stack,
+            records,
+        };
+
         loop {
-            trace!(
-                "Run \"{}\" | IP = {}",
-                active_record
-                    .name()
-                    .cloned()
-                    .unwrap_or_else(|| DustString::from("anonymous")),
-                active_record.ip
-            );
-
+            let active_record = thread_data.records.last_unchecked();
             let instruction = active_record.chunk.instructions[active_record.ip];
-            let action = RunAction::from(instruction);
-            let signal = (action.logic)(action.instruction, active_record);
+            let record_action = RecordAction::from(instruction);
+            let value_option = (record_action.logic)(record_action.instruction, &mut thread_data);
 
-            trace!("Thread Signal: {}", signal);
+            if thread_data.call_stack.is_empty() {
+                trace!("Returning {value_option:?} from function");
 
-            active_record.ip += 1;
-
-            match signal {
-                ThreadSignal::Continue => {}
-                ThreadSignal::LoadFunction {
-                    destination,
-                    prototype_index,
-                } => {
-                    let function_record_index = prototype_index as usize;
-                    let function = self.chunk.prototypes[function_record_index].as_function();
-                    let register = Register::Value(Value::Function(function));
-
-                    active_record.set_register(destination, register);
-                }
-                ThreadSignal::Call {
-                    function_register,
-                    return_register,
-                    argument_count,
-                } => {
-                    let function = active_record
-                        .open_register(function_register)
-                        .as_function()
-                        .unwrap();
-                    let first_argument_register = return_register - argument_count;
-                    let mut arguments = Vec::with_capacity(argument_count as usize);
-
-                    for register_index in first_argument_register..return_register {
-                        let value = active_record.clone_register_value_or_constant(register_index);
-
-                        arguments.push(value);
-                    }
-
-                    trace!("Passing arguments: {arguments:?}");
-
-                    let prototype = &self.chunk.prototypes[function.prototype_index as usize];
-                    let next_record = Record::new(prototype);
-                    let next_call = FunctionCall {
-                        name: next_record.name().cloned(),
-                        return_register,
-                        ip: active_record.ip,
-                    };
-
-                    call_stack.push(next_call);
-                    records.push(next_record);
-
-                    active_record = records.last_mut_unchecked();
-
-                    for (index, argument) in arguments.into_iter().enumerate() {
-                        active_record.set_register(index as u8, Register::Value(argument));
-                    }
-                }
-                ThreadSignal::Return {
-                    should_return_value,
-                    return_register,
-                } => {
-                    trace!("Returning with call stack:\n{call_stack}");
-
-                    let return_value = if should_return_value {
-                        Some(
-                            active_record
-                                .empty_register_or_clone_constant(return_register, Register::Empty),
-                        )
-                    } else {
-                        None
-                    };
-
-                    let current_call = call_stack.pop_unchecked();
-                    let _current_record = records.pop_unchecked();
-                    let destination = current_call.return_register;
-
-                    if call_stack.is_empty() {
-                        return if should_return_value {
-                            Some(return_value.unwrap())
-                        } else {
-                            None
-                        };
-                    }
-
-                    let outer_record = records.last_mut_unchecked();
-
-                    if should_return_value {
-                        outer_record
-                            .set_register(destination, Register::Value(return_value.unwrap()));
-                    }
-
-                    active_record = outer_record;
-                }
+                return value_option;
             }
         }
     }
 }
 
+#[derive(Debug)]
+pub struct ThreadData<'a> {
+    pub call_stack: Stack<FunctionCall>,
+    pub records: Stack<Record<'a>>,
+}
+
 #[derive(Debug)]
 pub enum ThreadSignal {
     Continue,