diff --git a/src/eval.rs b/src/eval.rs
index a3cfe54e13..5ff5242d02 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -1,4 +1,4 @@
-use std::{collections::HashMap, fmt::Display};
+use std::{cell::RefCell, collections::HashMap, fmt::Display, rc::Rc};
 
 use crate::{
     parser::Operator, Block, BlockId, Call, Expr, Expression, ParserState, Span, Statement, VarId,
@@ -59,13 +59,17 @@ pub struct State<'a> {
     pub parser_state: &'a ParserState,
 }
 
-pub struct Stack {
+pub struct StackFrame {
     pub vars: HashMap<VarId, Value>,
+    pub parent: Option<Stack>,
 }
 
-impl Stack {
-    pub fn get_var(&self, var_id: VarId) -> Result<Value, ShellError> {
-        match self.vars.get(&var_id) {
+pub type Stack = Rc<RefCell<StackFrame>>;
+
+impl StackFrame {
+    pub fn get_var(this: Stack, var_id: VarId) -> Result<Value, ShellError> {
+        let this = this.borrow();
+        match this.vars.get(&var_id) {
             Some(v) => Ok(v.clone()),
             _ => {
                 println!("var_id: {}", var_id);
@@ -74,14 +78,32 @@ impl Stack {
         }
     }
 
-    pub fn add_var(&mut self, var_id: VarId, value: Value) {
-        self.vars.insert(var_id, value);
+    pub fn add_var(this: Stack, var_id: VarId, value: Value) {
+        let mut this = this.borrow_mut();
+        this.vars.insert(var_id, value);
+    }
+
+    pub fn enter_scope(this: Stack) -> Stack {
+        Rc::new(RefCell::new(StackFrame {
+            vars: HashMap::new(),
+            parent: Some(this),
+        }))
+    }
+
+    pub fn print_stack(&self) {
+        println!("===frame===");
+        for (var, val) in &self.vars {
+            println!("{}: {:?}", var, val);
+        }
+        if let Some(parent) = &self.parent {
+            parent.borrow().print_stack()
+        }
     }
 }
 
 pub fn eval_operator(
     _state: &State,
-    _stack: &mut Stack,
+    _stack: Stack,
     op: &Expression,
 ) -> Result<Operator, ShellError> {
     match op {
@@ -93,7 +115,7 @@ pub fn eval_operator(
     }
 }
 
-fn eval_call(state: &State, stack: &mut Stack, call: &Call) -> Result<Value, ShellError> {
+fn eval_call(state: &State, stack: Stack, call: &Call) -> Result<Value, ShellError> {
     let decl = state.parser_state.get_decl(call.decl_id);
     if let Some(block_id) = decl.body {
         for (arg, param) in call
@@ -101,14 +123,15 @@ fn eval_call(state: &State, stack: &mut Stack, call: &Call) -> Result<Value, She
             .iter()
             .zip(decl.signature.required_positional.iter())
         {
-            let result = eval_expression(state, stack, arg)?;
+            let result = eval_expression(state, stack.clone(), arg)?;
             let var_id = param
                 .var_id
                 .expect("internal error: all custom parameters must have var_ids");
 
-            stack.add_var(var_id, result);
+            StackFrame::add_var(stack.clone(), var_id, result);
         }
         let block = state.parser_state.get_block(block_id);
+        let stack = StackFrame::enter_scope(stack);
         eval_block(state, stack, block)
     } else if decl.signature.name == "let" {
         let var_id = call.positional[0]
@@ -119,11 +142,11 @@ fn eval_call(state: &State, stack: &mut Stack, call: &Call) -> Result<Value, She
             .as_keyword()
             .expect("internal error: missing keyword");
 
-        let rhs = eval_expression(state, stack, keyword_expr)?;
+        let rhs = eval_expression(state, stack.clone(), keyword_expr)?;
 
         println!("Adding: {:?} to {}", rhs, var_id);
 
-        stack.add_var(var_id, rhs);
+        StackFrame::add_var(stack, var_id, rhs);
         Ok(Value::Unknown)
     } else if decl.signature.name == "if" {
         let cond = &call.positional[0];
@@ -132,17 +155,19 @@ fn eval_call(state: &State, stack: &mut Stack, call: &Call) -> Result<Value, She
             .expect("internal error: expected block");
         let else_case = call.positional.get(2);
 
-        let result = eval_expression(state, stack, cond)?;
+        let result = eval_expression(state, stack.clone(), cond)?;
         match result {
             Value::Bool { val, .. } => {
                 if val {
                     let block = state.parser_state.get_block(then_block);
+                    let stack = StackFrame::enter_scope(stack);
                     eval_block(state, stack, block)
                 } else if let Some(else_case) = else_case {
                     println!("{:?}", else_case);
                     if let Some(else_expr) = else_case.as_keyword() {
                         if let Some(block_id) = else_expr.as_block() {
                             let block = state.parser_state.get_block(block_id);
+                            let stack = StackFrame::enter_scope(stack);
                             eval_block(state, stack, block)
                         } else {
                             eval_expression(state, stack, else_expr)
@@ -160,7 +185,7 @@ fn eval_call(state: &State, stack: &mut Stack, call: &Call) -> Result<Value, She
         let mut output = vec![];
 
         for expr in &call.positional {
-            let val = eval_expression(state, stack, expr)?;
+            let val = eval_expression(state, stack.clone(), expr)?;
 
             output.push(val.to_string());
         }
@@ -175,7 +200,7 @@ fn eval_call(state: &State, stack: &mut Stack, call: &Call) -> Result<Value, She
 
 pub fn eval_expression(
     state: &State,
-    stack: &mut Stack,
+    stack: Stack,
     expr: &Expression,
 ) -> Result<Value, ShellError> {
     match &expr.expr {
@@ -187,13 +212,13 @@ pub fn eval_expression(
             val: *i,
             span: expr.span,
         }),
-        Expr::Var(var_id) => stack.get_var(*var_id),
+        Expr::Var(var_id) => StackFrame::get_var(stack, *var_id),
         Expr::Call(call) => eval_call(state, stack, call),
         Expr::ExternalCall(_, _) => Err(ShellError::Unsupported(expr.span)),
         Expr::Operator(_) => Ok(Value::Unknown),
         Expr::BinaryOp(lhs, op, rhs) => {
-            let lhs = eval_expression(state, stack, lhs)?;
-            let op = eval_operator(state, stack, op)?;
+            let lhs = eval_expression(state, stack.clone(), lhs)?;
+            let op = eval_operator(state, stack.clone(), op)?;
             let rhs = eval_expression(state, stack, rhs)?;
 
             match op {
@@ -205,13 +230,14 @@ pub fn eval_expression(
         Expr::Subexpression(block_id) => {
             let block = state.parser_state.get_block(*block_id);
 
+            let stack = StackFrame::enter_scope(stack);
             eval_block(state, stack, block)
         }
         Expr::Block(block_id) => Ok(Value::Block(*block_id)),
         Expr::List(x) => {
             let mut output = vec![];
             for expr in x {
-                output.push(eval_expression(state, stack, expr)?);
+                output.push(eval_expression(state, stack.clone(), expr)?);
             }
             Ok(Value::List(output))
         }
@@ -226,12 +252,12 @@ pub fn eval_expression(
     }
 }
 
-pub fn eval_block(state: &State, stack: &mut Stack, block: &Block) -> Result<Value, ShellError> {
+pub fn eval_block(state: &State, stack: Stack, block: &Block) -> Result<Value, ShellError> {
     let mut last = Ok(Value::Unknown);
 
     for stmt in &block.stmts {
         if let Statement::Expression(expression) = stmt {
-            last = Ok(eval_expression(state, stack, expression)?);
+            last = Ok(eval_expression(state, stack.clone(), expression)?);
         }
     }
 
diff --git a/src/lib.rs b/src/lib.rs
index 47915ab09d..12f5329c20 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -14,7 +14,7 @@ mod tests;
 mod type_check;
 
 pub use declaration::Declaration;
-pub use eval::{eval_block, eval_expression, Stack, State};
+pub use eval::{eval_block, eval_expression, Stack, StackFrame, State};
 pub use lex::{lex, Token, TokenContents};
 pub use lite_parse::{lite_parse, LiteBlock, LiteCommand, LiteStatement};
 pub use parse_error::ParseError;
diff --git a/src/main.rs b/src/main.rs
index 95c0d594b8..991e310e80 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,8 @@
 use std::{cell::RefCell, collections::HashMap, rc::Rc};
 
 use engine_q::{
-    eval_block, NuHighlighter, ParserState, ParserWorkingSet, Signature, Stack, State, SyntaxShape,
+    eval_block, NuHighlighter, ParserState, ParserWorkingSet, Signature, StackFrame, State,
+    SyntaxShape,
 };
 
 fn main() -> std::io::Result<()> {
@@ -73,6 +74,8 @@ fn main() -> std::io::Result<()> {
         working_set.add_decl(sig.into());
         let sig = Signature::build("blocks");
         working_set.add_decl(sig.into());
+        let sig = Signature::build("stack");
+        working_set.add_decl(sig.into());
 
         let sig = Signature::build("add");
         working_set.add_decl(sig.into());
@@ -131,9 +134,10 @@ fn main() -> std::io::Result<()> {
 
         let prompt = DefaultPrompt::new(1);
         let mut current_line = 1;
-        let mut stack = Stack {
+        let stack = Rc::new(RefCell::new(StackFrame {
             vars: HashMap::new(),
-        };
+            parent: None,
+        }));
 
         loop {
             let input = line_editor.read_line(&prompt)?;
@@ -150,6 +154,8 @@ fn main() -> std::io::Result<()> {
                     } else if s.trim() == "blocks" {
                         parser_state.borrow().print_blocks();
                         continue;
+                    } else if s.trim() == "stack" {
+                        stack.borrow().print_stack();
                     }
                     // println!("input: '{}'", s);
 
@@ -176,7 +182,7 @@ fn main() -> std::io::Result<()> {
                         parser_state: &*parser_state.borrow(),
                     };
 
-                    let output = eval_block(&state, &mut stack, &block);
+                    let output = eval_block(&state, stack.clone(), &block);
                     println!("{:#?}", output);
                 }
                 Signal::CtrlC => {