diff --git a/src/compiler/compiler.ts b/src/compiler/compiler.ts
index 7581f17..efcff49 100644
--- a/src/compiler/compiler.ts
+++ b/src/compiler/compiler.ts
@@ -9,6 +9,7 @@ import {
   checkTreeForErrors,
   getAllChildren,
   getAssignmentParts,
+  getCompoundAssignmentParts,
   getBinaryParts,
   getDotGetParts,
   getFunctionCallParts,
@@ -17,6 +18,7 @@ import {
   getNamedArgParts,
   getPipeExprParts,
   getStringParts,
+  getTryExprParts,
 } from '#compiler/utils'
 
 const DEBUG = false
@@ -51,6 +53,7 @@ export class Compiler {
   instructions: ProgramItem[] = []
   fnLabelCount = 0
   ifLabelCount = 0
+  tryLabelCount = 0
   bytecode: Bytecode
   pipeCounter = 0
 
@@ -265,6 +268,34 @@ export class Compiler {
         return instructions
       }
 
+      case terms.CompoundAssign: {
+        const { identifier, operator, right } = getCompoundAssignmentParts(node)
+        const identifierName = input.slice(identifier.from, identifier.to)
+        const instructions: ProgramItem[] = []
+
+        // will throw if undefined
+        instructions.push(['LOAD', identifierName])
+
+        instructions.push(...this.#compileNode(right, input))
+
+        const opValue = input.slice(operator.from, operator.to)
+        switch (opValue) {
+          case '+=': instructions.push(['ADD']); break
+          case '-=': instructions.push(['SUB']); break
+          case '*=': instructions.push(['MUL']); break
+          case '/=': instructions.push(['DIV']); break
+          case '%=': instructions.push(['MOD']); break
+          default:
+            throw new CompilerError(`Unknown compound operator: ${opValue}`, operator.from, operator.to)
+        }
+
+        // DUP and store (same as regular assignment)
+        instructions.push(['DUP'])
+        instructions.push(['STORE', identifierName])
+
+        return instructions
+      }
+
       case terms.ParenExpr: {
         const child = node.firstChild
         if (!child) return [] // I guess it is empty parentheses?
@@ -273,7 +304,10 @@ export class Compiler {
       }
 
       case terms.FunctionDef: {
-        const { paramNames, bodyNodes } = getFunctionDefParts(node, input)
+        const { paramNames, bodyNodes, catchVariable, catchBody, finallyBody } = getFunctionDefParts(
+          node,
+          input
+        )
         const instructions: ProgramItem[] = []
         const functionLabel: Label = `.func_${this.fnLabelCount++}`
         const afterLabel: Label = `.after_${functionLabel}`
@@ -281,9 +315,27 @@ export class Compiler {
         instructions.push(['JUMP', afterLabel])
 
         instructions.push([`${functionLabel}:`])
-        bodyNodes.forEach((bodyNode) => {
-          instructions.push(...this.#compileNode(bodyNode, input))
-        })
+
+        const compileFunctionBody = () => {
+          const bodyInstructions: ProgramItem[] = []
+          bodyNodes.forEach((bodyNode, index) => {
+            bodyInstructions.push(...this.#compileNode(bodyNode, input))
+            if (index < bodyNodes.length - 1) {
+              bodyInstructions.push(['POP'])
+            }
+          })
+          return bodyInstructions
+        }
+
+        if (catchVariable || finallyBody) {
+          // If function has catch or finally, wrap body in try/catch/finally
+          instructions.push(
+            ...this.#compileTryCatchFinally(compileFunctionBody, catchVariable, catchBody, finallyBody, input)
+          )
+        } else {
+          instructions.push(...compileFunctionBody())
+        }
+
         instructions.push(['RETURN'])
 
         instructions.push([`${afterLabel}:`])
@@ -337,10 +389,48 @@ export class Compiler {
       }
 
       case terms.ThenBlock:
-      case terms.SingleLineThenBlock: {
-        const instructions = getAllChildren(node)
-          .map((child) => this.#compileNode(child, input))
-          .flat()
+      case terms.SingleLineThenBlock:
+      case terms.TryBlock: {
+        const children = getAllChildren(node)
+        const instructions: ProgramItem[] = []
+
+        children.forEach((child, index) => {
+          instructions.push(...this.#compileNode(child, input))
+          // keep only the last expression's value
+          if (index < children.length - 1) {
+            instructions.push(['POP'])
+          }
+        })
+
+        return instructions
+      }
+
+      case terms.TryExpr: {
+        const { tryBlock, catchVariable, catchBody, finallyBody } = getTryExprParts(node, input)
+
+        return this.#compileTryCatchFinally(
+          () => this.#compileNode(tryBlock, input),
+          catchVariable,
+          catchBody,
+          finallyBody,
+          input
+        )
+      }
+
+      case terms.Throw: {
+        const children = getAllChildren(node)
+        const [_throwKeyword, expression] = children
+        if (!expression) {
+          throw new CompilerError(
+            `Throw expected expression, got ${children.length} children`,
+            node.from,
+            node.to
+          )
+        }
+
+        const instructions: ProgramItem[] = []
+        instructions.push(...this.#compileNode(expression, input))
+        instructions.push(['THROW'])
 
         return instructions
       }
@@ -547,4 +637,52 @@ export class Compiler {
         )
     }
   }
+
+  #compileTryCatchFinally(
+    compileTryBody: () => ProgramItem[],
+    catchVariable: string | undefined,
+    catchBody: SyntaxNode | undefined,
+    finallyBody: SyntaxNode | undefined,
+    input: string
+  ): ProgramItem[] {
+    const instructions: ProgramItem[] = []
+    this.tryLabelCount++
+    const catchLabel: Label = `.catch_${this.tryLabelCount}`
+    const finallyLabel: Label = finallyBody ? `.finally_${this.tryLabelCount}` : (null as any)
+    const endLabel: Label = `.end_try_${this.tryLabelCount}`
+
+    instructions.push(['PUSH_TRY', catchLabel])
+    instructions.push(...compileTryBody())
+    instructions.push(['POP_TRY'])
+    instructions.push(['JUMP', finallyBody ? finallyLabel : endLabel])
+
+    // catch block
+    instructions.push([`${catchLabel}:`])
+    if (catchBody && catchVariable) {
+      instructions.push(['STORE', catchVariable])
+      const catchInstructions = this.#compileNode(catchBody, input)
+      instructions.push(...catchInstructions)
+      instructions.push(['JUMP', finallyBody ? finallyLabel : endLabel])
+    } else {
+      // no catch block
+      if (finallyBody) {
+        instructions.push(['JUMP', finallyLabel])
+      } else {
+        instructions.push(['THROW'])
+      }
+    }
+
+    // finally block
+    if (finallyBody) {
+      instructions.push([`${finallyLabel}:`])
+      const finallyInstructions = this.#compileNode(finallyBody, input)
+      instructions.push(...finallyInstructions)
+      // finally doesn't return a value
+      instructions.push(['POP'])
+    }
+
+    instructions.push([`${endLabel}:`])
+
+    return instructions
+  }
 }
diff --git a/src/compiler/tests/exceptions.test.ts b/src/compiler/tests/exceptions.test.ts
new file mode 100644
index 0000000..9a71012
--- /dev/null
+++ b/src/compiler/tests/exceptions.test.ts
@@ -0,0 +1,311 @@
+import { describe } from 'bun:test'
+import { expect, test } from 'bun:test'
+
+describe('exception handling', () => {
+  test('try with catch - no error thrown', () => {
+    expect(`
+      try:
+        42
+      catch err:
+        99
+      end
+    `).toEvaluateTo(42)
+  })
+
+  test('try with catch - error thrown', () => {
+    expect(`
+      try:
+        throw 'something went wrong'
+        99
+      catch err:
+        err
+      end
+    `).toEvaluateTo('something went wrong')
+  })
+
+  test('try with catch - catch variable binding', () => {
+    expect(`
+      try:
+        throw 100
+      catch my-error:
+        my-error + 50
+      end
+    `).toEvaluateTo(150)
+  })
+
+  test('try with finally - no error', () => {
+    expect(`
+      x = 0
+      result = try:
+        x = 10
+        42
+      finally:
+        x = x + 5
+      end
+      x
+    `).toEvaluateTo(15)
+  })
+
+  test('try with finally - return value from try', () => {
+    expect(`
+      x = 0
+      result = try:
+        x = 10
+        42
+      finally:
+        x = x + 5
+        999
+      end
+      result
+    `).toEvaluateTo(42)
+  })
+
+  test('try with catch and finally - no error', () => {
+    expect(`
+      x = 0
+      try:
+        x = 10
+        42
+      catch err:
+        x = 999
+        0
+      finally:
+        x = x + 5
+      end
+      x
+    `).toEvaluateTo(15)
+  })
+
+  test('try with catch and finally - error thrown', () => {
+    expect(`
+      x = 0
+      result = try:
+        x = 10
+        throw 'error'
+        99
+      catch err:
+        x = 20
+        err
+      finally:
+        x = x + 5
+      end
+      x
+    `).toEvaluateTo(25)
+  })
+
+  test('try with catch and finally - return value from catch', () => {
+    expect(`
+      result = try:
+        throw 'oops'
+      catch err:
+        'caught'
+      finally:
+        'finally'
+      end
+      result
+    `).toEvaluateTo('caught')
+  })
+
+  test('throw statement with string', () => {
+    expect(`
+      try:
+        throw 'error message'
+      catch err:
+        err
+      end
+    `).toEvaluateTo('error message')
+  })
+
+  test('throw statement with number', () => {
+    expect(`
+      try:
+        throw 404
+      catch err:
+        err
+      end
+    `).toEvaluateTo(404)
+  })
+
+  test('throw statement with dict', () => {
+    expect(`
+      try:
+        throw [code=500 message=failed]
+      catch e:
+        e
+      end
+    `).toEvaluateTo({ code: 500, message: 'failed' })
+  })
+
+  test('uncaught exception fails', () => {
+    expect(`throw 'uncaught error'`).toFailEvaluation()
+  })
+
+  test('single-line try catch', () => {
+    expect(`result = try: throw 'err' catch e: 'handled' end; result`).toEvaluateTo('handled')
+  })
+
+  test('nested try blocks - inner catches', () => {
+    expect(`
+      try:
+        result = try:
+          throw 'inner error'
+        catch err:
+          err
+        end
+        result
+      catch outer:
+        'outer'
+      end
+    `).toEvaluateTo('inner error')
+  })
+
+  test('nested try blocks - outer catches', () => {
+    expect(`
+      try:
+        try:
+          throw 'inner error'
+        catch err:
+          throw 'outer error'
+        end
+      catch outer:
+        outer
+      end
+    `).toEvaluateTo('outer error')
+  })
+
+  test('try as expression', () => {
+    expect(`
+      x = try: 10 catch err: 0 end
+      y = try: throw 'err' catch err: 20 end
+      x + y
+    `).toEvaluateTo(30)
+  })
+})
+
+describe('function-level exception handling', () => {
+  test('function with catch - no error', () => {
+    expect(`
+      read-file = do path:
+        path
+      catch e:
+        'default'
+      end
+
+      read-file test.txt
+    `).toEvaluateTo('test.txt')
+  })
+
+  test('function with catch - error thrown', () => {
+    expect(`
+      read-file = do path:
+        throw 'file not found'
+      catch e:
+        'default'
+      end
+
+      read-file test.txt
+    `).toEvaluateTo('default')
+  })
+
+  test('function with catch - error variable binding', () => {
+    expect(`
+      safe-call = do:
+        throw 'operation failed'
+      catch err:
+        err
+      end
+
+      safe-call
+    `).toEvaluateTo('operation failed')
+  })
+
+  test('function with finally - always runs', () => {
+    expect(`
+      counter = 0
+      increment-task = do:
+        result = 42
+        result
+      finally:
+        counter = counter + 1
+      end
+
+      x = increment-task
+      y = increment-task
+      counter
+    `).toEvaluateTo(2)
+  })
+
+  test('function with finally - return value from body', () => {
+    expect(`
+      get-value = do:
+        100
+      finally:
+        999
+      end
+
+      get-value
+    `).toEvaluateTo(100)
+  })
+
+  test('function with catch and finally', () => {
+    expect(`
+      cleanup-count = 0
+      safe-op = do should-fail:
+        if should-fail:
+          throw 'failed'
+        end
+        'success'
+      catch e:
+        'caught'
+      finally:
+        cleanup-count = cleanup-count + 1
+      end
+
+      result1 = safe-op false
+      result2 = safe-op true
+      cleanup-count
+    `).toEvaluateTo(2)
+  })
+
+  test('function with catch and finally - catch return value', () => {
+    expect(`
+      safe-fail = do:
+        throw 'always fails'
+      catch e:
+        'error handled'
+      finally:
+        noop = 1
+      end
+
+      safe-fail
+    `).toEvaluateTo('error handled')
+  })
+
+  test('function without catch/finally still works', () => {
+    expect(`
+      regular = do x:
+        x + 10
+      end
+
+      regular 5
+    `).toEvaluateTo(15)
+  })
+
+  test('nested functions with catch', () => {
+    expect(`
+      inner = do:
+        throw 'inner error'
+      catch e:
+        'inner caught'
+      end
+
+      outer = do:
+        inner
+      catch e:
+        'outer caught'
+      end
+
+      outer
+    `).toEvaluateTo('inner caught')
+  })
+})
diff --git a/src/compiler/tests/native-exceptions.test.ts b/src/compiler/tests/native-exceptions.test.ts
new file mode 100644
index 0000000..f7e2e37
--- /dev/null
+++ b/src/compiler/tests/native-exceptions.test.ts
@@ -0,0 +1,292 @@
+import { describe, test, expect } from 'bun:test'
+import { Compiler } from '#compiler/compiler'
+import { VM } from 'reefvm'
+
+describe('Native Function Exceptions', () => {
+  test('native function error caught by try/catch', async () => {
+    const code = `
+      result = try:
+        failing-fn
+      catch e:
+        'caught: ' + e
+      end
+
+      result
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('failing-fn', () => {
+      throw new Error('native function failed')
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({ type: 'string', value: 'caught: native function failed' })
+  })
+
+  test('async native function error caught by try/catch', async () => {
+    const code = `
+      result = try:
+        async-fail
+      catch e:
+        'async caught: ' + e
+      end
+
+      result
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('async-fail', async () => {
+      await new Promise(resolve => setTimeout(resolve, 1))
+      throw new Error('async error')
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({ type: 'string', value: 'async caught: async error' })
+  })
+
+  test('native function with arguments throwing error', async () => {
+    const code = `
+      result = try:
+        read-file missing.txt
+      catch e:
+        'default content'
+      end
+
+      result
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('read-file', (path: string) => {
+      if (path === 'missing.txt') {
+        throw new Error('file not found')
+      }
+      return 'file contents'
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({ type: 'string', value: 'default content' })
+  })
+
+  test('native function error with finally block', async () => {
+    const code = `
+      cleanup-count = 0
+
+      result = try:
+        failing-fn
+      catch e:
+        'error handled'
+      finally:
+        cleanup-count = cleanup-count + 1
+      end
+
+      cleanup-count
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('failing-fn', () => {
+      throw new Error('native error')
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({ type: 'number', value: 1 })
+  })
+
+  test('native function error without catch propagates', async () => {
+    const code = `
+      failing-fn
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('failing-fn', () => {
+      throw new Error('uncaught error')
+    })
+
+    await expect(vm.run()).rejects.toThrow('uncaught error')
+  })
+
+  test('native function in function-level catch', async () => {
+    const code = `
+      safe-read = do path:
+        read-file path
+      catch e:
+        'default: ' + e
+      end
+
+      result = safe-read missing.txt
+      result
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('read-file', (path: string) => {
+      throw new Error('file not found: ' + path)
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({ type: 'string', value: 'default: file not found: missing.txt' })
+  })
+
+  test('nested native function errors', async () => {
+    const code = `
+      result = try:
+        try:
+          inner-fail
+        catch e:
+          throw 'wrapped: ' + e
+        end
+      catch e:
+        'outer caught: ' + e
+      end
+
+      result
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('inner-fail', () => {
+      throw new Error('inner error')
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({ type: 'string', value: 'outer caught: wrapped: inner error' })
+  })
+
+  test('native function error with multiple named args', async () => {
+    const code = `
+      result = try:
+        process-file path=missing.txt mode=strict
+      catch e:
+        'error: ' + e
+      end
+
+      result
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('process-file', (path: string, mode: string = 'lenient') => {
+      if (mode === 'strict' && path === 'missing.txt') {
+        throw new Error('strict mode: file required')
+      }
+      return 'processed'
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({ type: 'string', value: 'error: strict mode: file required' })
+  })
+
+  test('native function returning normally after other functions threw', async () => {
+    const code = `
+      result1 = try:
+        failing-fn
+      catch e:
+        'caught'
+      end
+
+      result2 = success-fn
+
+      result1 + ' then ' + result2
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('failing-fn', () => {
+      throw new Error('error')
+    })
+
+    vm.set('success-fn', () => {
+      return 'success'
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({ type: 'string', value: 'caught then success' })
+  })
+
+  test('native function error message preserved', async () => {
+    const code = `
+      result = try:
+        throw-custom-message
+      catch e:
+        e
+      end
+
+      result
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('throw-custom-message', () => {
+      throw new Error('This is a very specific error message with details')
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({
+      type: 'string',
+      value: 'This is a very specific error message with details'
+    })
+  })
+
+  test('native function throwing non-Error value', async () => {
+    const code = `
+      result = try:
+        throw-string
+      catch e:
+        'caught: ' + e
+      end
+
+      result
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('throw-string', () => {
+      throw 'plain string error'
+    })
+
+    const result = await vm.run()
+    expect(result).toEqual({ type: 'string', value: 'caught: plain string error' })
+  })
+
+  test('multiple native function calls with mixed success/failure', async () => {
+    const code = `
+      r1 = try: success-fn catch e: 'error' end
+      r2 = try: failing-fn catch e: 'caught' end
+      r3 = try: success-fn catch e: 'error' end
+
+      results = [r1 r2 r3]
+      results
+    `
+
+    const compiler = new Compiler(code)
+    const vm = new VM(compiler.bytecode)
+
+    vm.set('success-fn', () => 'ok')
+    vm.set('failing-fn', () => {
+      throw new Error('failed')
+    })
+
+    const result = await vm.run()
+    expect(result.type).toBe('array')
+    const arr = result.value as any[]
+    expect(arr.length).toBe(3)
+    expect(arr[0]).toEqual({ type: 'string', value: 'ok' })
+    expect(arr[1]).toEqual({ type: 'string', value: 'caught' })
+    expect(arr[2]).toEqual({ type: 'string', value: 'ok' })
+  })
+})
diff --git a/src/compiler/utils.ts b/src/compiler/utils.ts
index 99b56c6..1f8f0c1 100644
--- a/src/compiler/utils.ts
+++ b/src/compiler/utils.ts
@@ -65,13 +65,34 @@ export const getAssignmentParts = (node: SyntaxNode) => {
   return { identifier: left, right }
 }
 
+export const getCompoundAssignmentParts = (node: SyntaxNode) => {
+  const children = getAllChildren(node)
+  const [left, operator, right] = children
+
+  if (!left || left.type.id !== terms.AssignableIdentifier) {
+    throw new CompilerError(
+      `CompoundAssign left child must be an AssignableIdentifier, got ${left ? left.type.name : 'none'}`,
+      node.from,
+      node.to
+    )
+  } else if (!operator || !right) {
+    throw new CompilerError(
+      `CompoundAssign expected 3 children, got ${children.length}`,
+      node.from,
+      node.to
+    )
+  }
+
+  return { identifier: left, operator, right }
+}
+
 export const getFunctionDefParts = (node: SyntaxNode, input: string) => {
   const children = getAllChildren(node)
-  const [fnKeyword, paramsNode, colon, ...bodyNodes] = children
+  const [fnKeyword, paramsNode, colon, ...rest] = children
 
-  if (!fnKeyword || !paramsNode || !colon || !bodyNodes) {
+  if (!fnKeyword || !paramsNode || !colon || !rest) {
     throw new CompilerError(
-      `FunctionDef expected 5 children, got ${children.length}`,
+      `FunctionDef expected at least 4 children, got ${children.length}`,
       node.from,
       node.to
     )
@@ -88,8 +109,48 @@ export const getFunctionDefParts = (node: SyntaxNode, input: string) => {
     return input.slice(param.from, param.to)
   })
 
-  const bodyWithoutEnd = bodyNodes.slice(0, -1)
-  return { paramNames, bodyNodes: bodyWithoutEnd }
+  // Separate body nodes from catch/finally/end
+  const bodyNodes: SyntaxNode[] = []
+  let catchExpr: SyntaxNode | undefined
+  let catchVariable: string | undefined
+  let catchBody: SyntaxNode | undefined
+  let finallyExpr: SyntaxNode | undefined
+  let finallyBody: SyntaxNode | undefined
+
+  for (const child of rest) {
+    if (child.type.id === terms.CatchExpr) {
+      catchExpr = child
+      const catchChildren = getAllChildren(child)
+      const [_catchKeyword, identifierNode, _colon, body] = catchChildren
+      if (!identifierNode || !body) {
+        throw new CompilerError(
+          `CatchExpr expected identifier and body, got ${catchChildren.length} children`,
+          child.from,
+          child.to
+        )
+      }
+      catchVariable = input.slice(identifierNode.from, identifierNode.to)
+      catchBody = body
+    } else if (child.type.id === terms.FinallyExpr) {
+      finallyExpr = child
+      const finallyChildren = getAllChildren(child)
+      const [_finallyKeyword, _colon, body] = finallyChildren
+      if (!body) {
+        throw new CompilerError(
+          `FinallyExpr expected body, got ${finallyChildren.length} children`,
+          child.from,
+          child.to
+        )
+      }
+      finallyBody = body
+    } else if (child.type.name === 'keyword' && input.slice(child.from, child.to) === 'end') {
+      // Skip the end keyword
+    } else {
+      bodyNodes.push(child)
+    }
+  }
+
+  return { paramNames, bodyNodes, catchVariable, catchBody, finallyBody }
 }
 
 export const getFunctionCallParts = (node: SyntaxNode, input: string) => {
@@ -204,7 +265,12 @@ export const getStringParts = (node: SyntaxNode, input: string) => {
     }
   })
 
-  return { parts, hasInterpolation: parts.length > 0 }
+  // hasInterpolation means the string has interpolation ($var) or escape sequences (\n)
+  // A simple string like 'hello' has one StringFragment but no interpolation
+  const hasInterpolation = parts.some(
+    (p) => p.type.id === terms.Interpolation || p.type.id === terms.EscapeSeq
+  )
+  return { parts, hasInterpolation }
 }
 
 export const getDotGetParts = (node: SyntaxNode, input: string) => {
@@ -239,3 +305,62 @@ export const getDotGetParts = (node: SyntaxNode, input: string) => {
 
   return { objectName, property }
 }
+
+export const getTryExprParts = (node: SyntaxNode, input: string) => {
+  const children = getAllChildren(node)
+
+  // First child is always 'try' keyword, second is colon, third is TryBlock or statement
+  const [tryKeyword, _colon, tryBlock, ...rest] = children
+
+  if (!tryKeyword || !tryBlock) {
+    throw new CompilerError(
+      `TryExpr expected at least 3 children, got ${children.length}`,
+      node.from,
+      node.to
+    )
+  }
+
+  let catchExpr: SyntaxNode | undefined
+  let catchVariable: string | undefined
+  let catchBody: SyntaxNode | undefined
+  let finallyExpr: SyntaxNode | undefined
+  let finallyBody: SyntaxNode | undefined
+
+  rest.forEach((child) => {
+    if (child.type.id === terms.CatchExpr) {
+      catchExpr = child
+      const catchChildren = getAllChildren(child)
+      const [_catchKeyword, identifierNode, _colon, body] = catchChildren
+      if (!identifierNode || !body) {
+        throw new CompilerError(
+          `CatchExpr expected identifier and body, got ${catchChildren.length} children`,
+          child.from,
+          child.to
+        )
+      }
+      catchVariable = input.slice(identifierNode.from, identifierNode.to)
+      catchBody = body
+    } else if (child.type.id === terms.FinallyExpr) {
+      finallyExpr = child
+      const finallyChildren = getAllChildren(child)
+      const [_finallyKeyword, _colon, body] = finallyChildren
+      if (!body) {
+        throw new CompilerError(
+          `FinallyExpr expected body, got ${finallyChildren.length} children`,
+          child.from,
+          child.to
+        )
+      }
+      finallyBody = body
+    }
+  })
+
+  return {
+    tryBlock,
+    catchExpr,
+    catchVariable,
+    catchBody,
+    finallyExpr,
+    finallyBody,
+  }
+}
diff --git a/src/parser/operatorTokenizer.ts b/src/parser/operatorTokenizer.ts
index ee1dc44..3c85400 100644
--- a/src/parser/operatorTokenizer.ts
+++ b/src/parser/operatorTokenizer.ts
@@ -10,7 +10,14 @@ const operators: Array<Operator> = [
   { str: '!=', tokenName: 'Neq' },
   { str: '==', tokenName: 'EqEq' },
 
-  // // Single-char operators
+  // Compound assignment operators (must come before single-char operators)
+  { str: '+=', tokenName: 'PlusEq' },
+  { str: '-=', tokenName: 'MinusEq' },
+  { str: '*=', tokenName: 'StarEq' },
+  { str: '/=', tokenName: 'SlashEq' },
+  { str: '%=', tokenName: 'ModuloEq' },
+
+  // Single-char operators
   { str: '*', tokenName: 'Star' },
   { str: '=', tokenName: 'Eq' },
   { str: '/', tokenName: 'Slash' },
diff --git a/src/parser/shrimp.grammar b/src/parser/shrimp.grammar
index 01c82f0..af3069d 100644
--- a/src/parser/shrimp.grammar
+++ b/src/parser/shrimp.grammar
@@ -6,7 +6,7 @@
 
 @top Program { item* }
 
-@external tokens operatorTokenizer from "./operatorTokenizer" { Star, Slash, Plus, Minus, And, Or, Eq, EqEq, Neq, Lt, Lte, Gt, Gte, Modulo }
+@external tokens operatorTokenizer from "./operatorTokenizer" { Star, Slash, Plus, Minus, And, Or, Eq, EqEq, Neq, Lt, Lte, Gt, Gte, Modulo, PlusEq, MinusEq, StarEq, SlashEq, ModuloEq }
 
 @tokens {
   @precedence { Number Regex }
@@ -51,8 +51,11 @@ item {
 consumeToTerminator {
   PipeExpr |
   ambiguousFunctionCall |
+  TryExpr |
+  Throw |
   IfExpr |
   FunctionDef |
+  CompoundAssign |
   Assign |
   BinOp |
   ConditionalOp |
@@ -97,11 +100,11 @@ FunctionDef {
 }
 
 singleLineFunctionDef {
-  Do Params colon consumeToTerminator @specialize[@name=keyword]<Identifier, "end">
+  Do Params colon consumeToTerminator CatchExpr? FinallyExpr? @specialize[@name=keyword]<Identifier, "end">
 }
 
 multilineFunctionDef {
-  Do Params colon newlineOrSemicolon block @specialize[@name=keyword]<Identifier, "end">
+  Do Params colon newlineOrSemicolon block CatchExpr? FinallyExpr? @specialize[@name=keyword]<Identifier, "end">
 }
 
 IfExpr {
@@ -129,7 +132,35 @@ ThenBlock {
 }
 
 SingleLineThenBlock {
-  consumeToTerminator 
+  consumeToTerminator
+}
+
+TryExpr {
+  singleLineTry | multilineTry
+}
+
+singleLineTry {
+  @specialize[@name=keyword]<Identifier, "try"> colon consumeToTerminator CatchExpr? FinallyExpr? @specialize[@name=keyword]<Identifier, "end">
+}
+
+multilineTry {
+  @specialize[@name=keyword]<Identifier, "try"> colon newlineOrSemicolon TryBlock CatchExpr? FinallyExpr? @specialize[@name=keyword]<Identifier, "end">
+}
+
+CatchExpr {
+  @specialize[@name=keyword]<Identifier, "catch"> Identifier colon (newlineOrSemicolon TryBlock | consumeToTerminator)
+}
+
+FinallyExpr {
+  @specialize[@name=keyword]<Identifier, "finally"> colon (newlineOrSemicolon TryBlock | consumeToTerminator)
+}
+
+TryBlock {
+  block
+}
+
+Throw {
+  @specialize[@name=keyword]<Identifier, "throw"> (BinOp | ConditionalOp | expression)
 }
 
 ConditionalOp {
@@ -151,6 +182,10 @@ Assign {
   (AssignableIdentifier | Array) Eq consumeToTerminator
 }
 
+CompoundAssign {
+  AssignableIdentifier (PlusEq | MinusEq | StarEq | SlashEq | ModuloEq) consumeToTerminator
+}
+
 BinOp {
   expression !multiplicative Modulo expression |
   (expression | BinOp) !multiplicative Star (expression | BinOp) |
diff --git a/src/parser/shrimp.terms.ts b/src/parser/shrimp.terms.ts
index 144d69b..ab4011b 100644
--- a/src/parser/shrimp.terms.ts
+++ b/src/parser/shrimp.terms.ts
@@ -14,40 +14,51 @@ export const
   Gt = 12,
   Gte = 13,
   Modulo = 14,
-  Identifier = 15,
-  AssignableIdentifier = 16,
-  Word = 17,
-  IdentifierBeforeDot = 18,
-  Do = 19,
-  Program = 20,
-  PipeExpr = 21,
-  FunctionCall = 22,
-  DotGet = 23,
-  Number = 24,
-  ParenExpr = 25,
-  FunctionCallOrIdentifier = 26,
-  BinOp = 27,
-  String = 28,
-  StringFragment = 29,
-  Interpolation = 30,
-  EscapeSeq = 31,
-  Boolean = 32,
-  Regex = 33,
-  Dict = 34,
-  NamedArg = 35,
-  NamedArgPrefix = 36,
-  FunctionDef = 37,
-  Params = 38,
-  colon = 39,
-  keyword = 54,
-  Underscore = 41,
-  Array = 42,
-  Null = 43,
-  ConditionalOp = 44,
-  PositionalArg = 45,
-  IfExpr = 47,
-  SingleLineThenBlock = 49,
-  ThenBlock = 50,
-  ElseIfExpr = 51,
-  ElseExpr = 53,
-  Assign = 55
+  PlusEq = 15,
+  MinusEq = 16,
+  StarEq = 17,
+  SlashEq = 18,
+  ModuloEq = 19,
+  Identifier = 20,
+  AssignableIdentifier = 21,
+  Word = 22,
+  IdentifierBeforeDot = 23,
+  Do = 24,
+  Program = 25,
+  PipeExpr = 26,
+  FunctionCall = 27,
+  DotGet = 28,
+  Number = 29,
+  ParenExpr = 30,
+  FunctionCallOrIdentifier = 31,
+  BinOp = 32,
+  String = 33,
+  StringFragment = 34,
+  Interpolation = 35,
+  EscapeSeq = 36,
+  Boolean = 37,
+  Regex = 38,
+  Dict = 39,
+  NamedArg = 40,
+  NamedArgPrefix = 41,
+  FunctionDef = 42,
+  Params = 43,
+  colon = 44,
+  CatchExpr = 45,
+  keyword = 68,
+  TryBlock = 47,
+  FinallyExpr = 48,
+  Underscore = 51,
+  Array = 52,
+  Null = 53,
+  ConditionalOp = 54,
+  PositionalArg = 55,
+  TryExpr = 57,
+  Throw = 59,
+  IfExpr = 61,
+  SingleLineThenBlock = 63,
+  ThenBlock = 64,
+  ElseIfExpr = 65,
+  ElseExpr = 67,
+  CompoundAssign = 69,
+  Assign = 70
diff --git a/src/parser/tests/basics.test.ts b/src/parser/tests/basics.test.ts
index a9fac46..d890f91 100644
--- a/src/parser/tests/basics.test.ts
+++ b/src/parser/tests/basics.test.ts
@@ -532,6 +532,72 @@ describe('Assign', () => {
   })
 })
 
+describe('CompoundAssign', () => {
+  test('parses += operator', () => {
+    expect('x += 5').toMatchTree(`
+      CompoundAssign
+        AssignableIdentifier x
+        PlusEq +=
+        Number 5`)
+  })
+
+  test('parses -= operator', () => {
+    expect('count -= 1').toMatchTree(`
+      CompoundAssign
+        AssignableIdentifier count
+        MinusEq -=
+        Number 1`)
+  })
+
+  test('parses *= operator', () => {
+    expect('total *= 2').toMatchTree(`
+      CompoundAssign
+        AssignableIdentifier total
+        StarEq *=
+        Number 2`)
+  })
+
+  test('parses /= operator', () => {
+    expect('value /= 10').toMatchTree(`
+      CompoundAssign
+        AssignableIdentifier value
+        SlashEq /=
+        Number 10`)
+  })
+
+  test('parses %= operator', () => {
+    expect('remainder %= 3').toMatchTree(`
+      CompoundAssign
+        AssignableIdentifier remainder
+        ModuloEq %=
+        Number 3`)
+  })
+
+  test('parses compound assignment with expression', () => {
+    expect('x += 1 + 2').toMatchTree(`
+      CompoundAssign
+        AssignableIdentifier x
+        PlusEq +=
+        BinOp
+          Number 1
+          Plus +
+          Number 2`)
+  })
+
+  test('parses compound assignment with function call', () => {
+    expect('total += add 5 3').toMatchTree(`
+      CompoundAssign
+        AssignableIdentifier total
+        PlusEq +=
+        FunctionCall
+          Identifier add
+          PositionalArg
+            Number 5
+          PositionalArg
+            Number 3`)
+  })
+})
+
 describe('DotGet whitespace sensitivity', () => {
   test('no whitespace - DotGet works when identifier in scope', () => {
     expect('basename = 5; basename.prop').toMatchTree(`
diff --git a/src/parser/tests/exceptions.test.ts b/src/parser/tests/exceptions.test.ts
new file mode 100644
index 0000000..039a279
--- /dev/null
+++ b/src/parser/tests/exceptions.test.ts
@@ -0,0 +1,278 @@
+import { expect, describe, test } from 'bun:test'
+
+import '../shrimp.grammar' // Importing this so changes cause it to retest!
+
+describe('try/catch/finally/throw', () => {
+  test('parses try with catch', () => {
+    expect(`try:
+      risky-operation
+    catch err:
+      handle-error err
+    end`).toMatchTree(`
+      TryExpr
+        keyword try
+        colon :
+        TryBlock
+          FunctionCallOrIdentifier
+            Identifier risky-operation
+        CatchExpr
+          keyword catch
+          Identifier err
+          colon :
+          TryBlock
+            FunctionCall
+              Identifier handle-error
+              PositionalArg
+                Identifier err
+        keyword end
+    `)
+  })
+
+  test('parses try with finally', () => {
+    expect(`try:
+      do-work
+    finally:
+      cleanup
+    end`).toMatchTree(`
+      TryExpr
+        keyword try
+        colon :
+        TryBlock
+          FunctionCallOrIdentifier
+            Identifier do-work
+        FinallyExpr
+          keyword finally
+          colon :
+          TryBlock
+            FunctionCallOrIdentifier
+              Identifier cleanup
+        keyword end
+    `)
+  })
+
+  test('parses try with catch and finally', () => {
+    expect(`try:
+      risky-operation
+    catch err:
+      handle-error err
+    finally:
+      cleanup
+    end`).toMatchTree(`
+      TryExpr
+        keyword try
+        colon :
+        TryBlock
+          FunctionCallOrIdentifier
+            Identifier risky-operation
+        CatchExpr
+          keyword catch
+          Identifier err
+          colon :
+          TryBlock
+            FunctionCall
+              Identifier handle-error
+              PositionalArg
+                Identifier err
+        FinallyExpr
+          keyword finally
+          colon :
+          TryBlock
+            FunctionCallOrIdentifier
+              Identifier cleanup
+        keyword end
+    `)
+  })
+
+  test('parses single-line try with catch', () => {
+    expect('result = try: parse-number input catch err: 0 end').toMatchTree(`
+      Assign
+        AssignableIdentifier result
+        Eq =
+        TryExpr
+          keyword try
+          colon :
+          FunctionCall
+            Identifier parse-number
+            PositionalArg
+              Identifier input
+          CatchExpr
+            keyword catch
+            Identifier err
+            colon :
+            Number 0
+          keyword end
+    `)
+  })
+
+  test('parses single-line try with finally', () => {
+    expect('try: work catch err: 0 finally: cleanup end').toMatchTree(`
+      TryExpr
+        keyword try
+        colon :
+        FunctionCallOrIdentifier
+          Identifier work
+        CatchExpr
+          keyword catch
+          Identifier err
+          colon :
+          Number 0
+        FinallyExpr
+          keyword finally
+          colon :
+          FunctionCallOrIdentifier
+            Identifier cleanup
+        keyword end
+    `)
+  })
+
+  test('parses throw statement with string', () => {
+    expect("throw 'error message'").toMatchTree(`
+      Throw
+        keyword throw
+        String
+          StringFragment error message
+    `)
+  })
+
+  test('parses throw statement with identifier', () => {
+    expect('throw error-object').toMatchTree(`
+      Throw
+        keyword throw
+        Identifier error-object
+    `)
+  })
+
+  test('parses throw statement with dict', () => {
+    expect('throw [type=validation-error message=failed]').toMatchTree(`
+      Throw
+        keyword throw
+        Dict
+          NamedArg
+            NamedArgPrefix type=
+            Identifier validation-error
+          NamedArg
+            NamedArgPrefix message=
+            Identifier failed
+    `)
+  })
+
+  test('does not parse identifiers that start with try', () => {
+    expect('trying = try: work catch err: 0 end').toMatchTree(`
+      Assign
+        AssignableIdentifier trying
+        Eq =
+        TryExpr
+          keyword try
+          colon :
+          FunctionCallOrIdentifier
+            Identifier work
+          CatchExpr
+            keyword catch
+            Identifier err
+            colon :
+            Number 0
+          keyword end
+    `)
+  })
+})
+
+describe('function-level exception handling', () => {
+  test('parses function with catch', () => {
+    expect(`read-file = do path:
+      read-data path
+    catch e:
+      empty-string
+    end`).toMatchTree(`
+      Assign
+        AssignableIdentifier read-file
+        Eq =
+        FunctionDef
+          Do do
+          Params
+            Identifier path
+          colon :
+          FunctionCall
+            Identifier read-data
+            PositionalArg
+              Identifier path
+          CatchExpr
+            keyword catch
+            Identifier e
+            colon :
+            TryBlock
+              FunctionCallOrIdentifier
+                Identifier empty-string
+          keyword end
+    `)
+  })
+
+  test('parses function with finally', () => {
+    expect(`cleanup-task = do x:
+      do-work x
+    finally:
+      close-resources
+    end`).toMatchTree(`
+      Assign
+        AssignableIdentifier cleanup-task
+        Eq =
+        FunctionDef
+          Do do
+          Params
+            Identifier x
+          colon :
+          FunctionCall
+            Identifier do-work
+            PositionalArg
+              Identifier x
+          FinallyExpr
+            keyword finally
+            colon :
+            TryBlock
+              FunctionCallOrIdentifier
+                Identifier close-resources
+          keyword end
+    `)
+  })
+
+  test('parses function with catch and finally', () => {
+    expect(`safe-operation = do x:
+      risky-work x
+    catch err:
+      log err
+      default-value
+    finally:
+      cleanup
+    end`).toMatchTree(`
+      Assign
+        AssignableIdentifier safe-operation
+        Eq =
+        FunctionDef
+          Do do
+          Params
+            Identifier x
+          colon :
+          FunctionCall
+            Identifier risky-work
+            PositionalArg
+              Identifier x
+          CatchExpr
+            keyword catch
+            Identifier err
+            colon :
+            TryBlock
+              FunctionCall
+                Identifier log
+                PositionalArg
+                  Identifier err
+              FunctionCallOrIdentifier
+                Identifier default-value
+          FinallyExpr
+            keyword finally
+            colon :
+            TryBlock
+              FunctionCallOrIdentifier
+                Identifier cleanup
+          keyword end
+    `)
+  })
+})
diff --git a/src/parser/tokenizer.ts b/src/parser/tokenizer.ts
index e4fc895..cbaac67 100644
--- a/src/parser/tokenizer.ts
+++ b/src/parser/tokenizer.ts
@@ -184,6 +184,17 @@ const chooseIdentifierToken = (input: InputStream, stack: Stack): number => {
   }
 
   const nextCh = getFullCodePoint(input, peekPos)
+  const nextCh2 = getFullCodePoint(input, peekPos + 1)
+
+  // Check for compound assignment operators: +=, -=, *=, /=, %=
+  if ([43/* + */, 45/* - */, 42/* * */, 47/* / */, 37/* % */].includes(nextCh) && nextCh2 === 61/* = */) {
+    // Found compound operator, check if it's followed by whitespace
+    const charAfterOp = getFullCodePoint(input, peekPos + 2)
+    if (isWhiteSpace(charAfterOp) || charAfterOp === -1 /* EOF */) {
+      return AssignableIdentifier
+    }
+  }
+
   if (nextCh === 61 /* = */) {
     // Found '=', but check if it's followed by whitespace
     // If '=' is followed by non-whitespace (like '=cool*'), it won't be tokenized as Eq
diff --git a/src/prelude/index.ts b/src/prelude/index.ts
index facf4b8..cc46ead 100644
--- a/src/prelude/index.ts
+++ b/src/prelude/index.ts
@@ -39,7 +39,7 @@ export const globals = {
     switch (value.type) {
       case 'string': case 'array': return value.value.length
       case 'dict': return value.value.size
-      default: return 0
+      default: throw new Error(`length: expected string, array, or dict, got ${value.type}`)
     }
   },
 
@@ -65,7 +65,24 @@ export const globals = {
   identity: (v: any) => v,
 
   // collections
-  at: (collection: any, index: number | string) => collection[index],
+  at: (collection: any, index: number | string) => {
+    const value = toValue(collection)
+    if (value.type === 'string' || value.type === 'array') {
+      const idx = typeof index === 'number' ? index : parseInt(index as string)
+      if (idx < 0 || idx >= value.value.length) {
+        throw new Error(`at: index ${idx} out of bounds for ${value.type} of length ${value.value.length}`)
+      }
+      return value.value[idx]
+    } else if (value.type === 'dict') {
+      const key = String(index)
+      if (!value.value.has(key)) {
+        throw new Error(`at: key '${key}' not found in dict`)
+      }
+      return value.value.get(key)
+    } else {
+      throw new Error(`at: expected string, array, or dict, got ${value.type}`)
+    }
+  },
   range: (start: number, end: number | null) => {
     if (end === null) {
       end = start
diff --git a/src/prelude/list.ts b/src/prelude/list.ts
index eb013ef..1f0ec76 100644
--- a/src/prelude/list.ts
+++ b/src/prelude/list.ts
@@ -1,3 +1,5 @@
+import { type Value, toValue, toNull } from 'reefvm'
+
 export const list = {
   slice: (list: any[], start: number, end?: number) => list.slice(start, end),
   map: async (list: any[], cb: Function) => {
@@ -40,9 +42,41 @@ export const list = {
     return true
   },
 
+  // mutating
+  push: (list: Value, item: Value) => {
+    if (list.type !== 'array') return toNull()
+    return toValue(list.value.push(item))
+  },
+  pop: (list: Value) => {
+    if (list.type !== 'array') return toNull()
+    return toValue(list.value.pop())
+  },
+  shift: (list: Value) => {
+    if (list.type !== 'array') return toNull()
+    return toValue(list.value.shift())
+  },
+  unshift: (list: Value, item: Value) => {
+    if (list.type !== 'array') return toNull()
+    return toValue(list.value.unshift(item))
+  },
+  splice: (list: Value, start: Value, deleteCount: Value, ...items: Value[]) => {
+    const realList = list.value as any[]
+    const realStart = start.value as number
+    const realDeleteCount = deleteCount.value as number
+    const realItems = items.map(item => item.value)
+    return toValue(realList.splice(realStart, realDeleteCount, ...realItems))
+  },
+
   // sequence operations
   reverse: (list: any[]) => list.slice().reverse(),
-  sort: (list: any[], cb?: (a: any, b: any) => number) => list.slice().sort(cb),
+  sort: async (list: any[], cb?: (a: any, b: any) => number) => {
+    const arr = [...list]
+    if (!cb) return arr.sort()
+    for (let i = 0; i < arr.length; i++)
+      for (let j = i + 1; j < arr.length; j++)
+        if ((await cb(arr[i], arr[j])) > 0) [arr[i], arr[j]] = [arr[j], arr[i]]
+    return arr
+  },
   concat: (...lists: any[][]) => lists.flat(1),
   flatten: (list: any[], depth: number = 1) => list.flat(depth),
   unique: (list: any[]) => Array.from(new Set(list)),
@@ -52,8 +86,14 @@ export const list = {
   first: (list: any[]) => list[0] ?? null,
   last: (list: any[]) => list[list.length - 1] ?? null,
   rest: (list: any[]) => list.slice(1),
-  take: (list: any[], n: number) => list.slice(0, n),
-  drop: (list: any[], n: number) => list.slice(n),
+  take: (list: any[], n: number) => {
+    if (n < 0) throw new Error(`take: count must be non-negative, got ${n}`)
+    return list.slice(0, n)
+  },
+  drop: (list: any[], n: number) => {
+    if (n < 0) throw new Error(`drop: count must be non-negative, got ${n}`)
+    return list.slice(n)
+  },
   append: (list: any[], item: any) => [...list, item],
   prepend: (list: any[], item: any) => [item, ...list],
   'index-of': (list: any[], item: any) => list.indexOf(item),
@@ -86,4 +126,13 @@ export const list = {
     }
     return groups
   },
-}
\ No newline at end of file
+}
+
+
+  // raw functions deal directly in Value types, meaning we can modify collection
+  // careful - they MUST return a Value!
+  ; (list.splice as any).raw = true
+  ; (list.push as any).raw = true
+  ; (list.pop as any).raw = true
+  ; (list.shift as any).raw = true
+  ; (list.unshift as any).raw = true
\ No newline at end of file
diff --git a/src/prelude/math.ts b/src/prelude/math.ts
index 21f2f57..148cde9 100644
--- a/src/prelude/math.ts
+++ b/src/prelude/math.ts
@@ -3,12 +3,24 @@ export const math = {
   floor: (n: number) => Math.floor(n),
   ceil: (n: number) => Math.ceil(n),
   round: (n: number) => Math.round(n),
-  min: (...nums: number[]) => Math.min(...nums),
-  max: (...nums: number[]) => Math.max(...nums),
+  min: (...nums: number[]) => {
+    if (nums.length === 0) throw new Error('min: expected at least one argument')
+    return Math.min(...nums)
+  },
+  max: (...nums: number[]) => {
+    if (nums.length === 0) throw new Error('max: expected at least one argument')
+    return Math.max(...nums)
+  },
   pow: (base: number, exp: number) => Math.pow(base, exp),
-  sqrt: (n: number) => Math.sqrt(n),
+  sqrt: (n: number) => {
+    if (n < 0) throw new Error(`sqrt: cannot take square root of negative number ${n}`)
+    return Math.sqrt(n)
+  },
   random: () => Math.random(),
-  clamp: (n: number, min: number, max: number) => Math.min(Math.max(n, min), max),
+  clamp: (n: number, min: number, max: number) => {
+    if (min > max) throw new Error(`clamp: min (${min}) must be less than or equal to max (${max})`)
+    return Math.min(Math.max(n, min), max)
+  },
   sign: (n: number) => Math.sign(n),
   trunc: (n: number) => Math.trunc(n),
 
diff --git a/src/prelude/str.ts b/src/prelude/str.ts
index fa0d657..5aede56 100644
--- a/src/prelude/str.ts
+++ b/src/prelude/str.ts
@@ -21,7 +21,11 @@ export const str = {
   'replace-all': (str: string, search: string, replacement: string) => str.replaceAll(search, replacement),
   slice: (str: string, start: number, end?: number | null) => str.slice(start, end ?? undefined),
   substring: (str: string, start: number, end?: number | null) => str.substring(start, end ?? undefined),
-  repeat: (str: string, count: number) => str.repeat(count),
+  repeat: (str: string, count: number) => {
+    if (count < 0) throw new Error(`repeat: count must be non-negative, got ${count}`)
+    if (!Number.isInteger(count)) throw new Error(`repeat: count must be an integer, got ${count}`)
+    return str.repeat(count)
+  },
   'pad-start': (str: string, length: number, pad: string = ' ') => str.padStart(length, pad),
   'pad-end': (str: string, length: number, pad: string = ' ') => str.padEnd(length, pad),
   lines: (str: string) => str.split('\n'),
diff --git a/src/prelude/tests/prelude.test.ts b/src/prelude/tests/prelude.test.ts
index ef7d8d6..40b7809 100644
--- a/src/prelude/tests/prelude.test.ts
+++ b/src/prelude/tests/prelude.test.ts
@@ -176,9 +176,12 @@ describe('introspection', () => {
     await expect(`length 'hello'`).toEvaluateTo(5, globals)
     await expect(`length [1 2 3]`).toEvaluateTo(3, globals)
     await expect(`length [a=1 b=2]`).toEvaluateTo(2, globals)
-    await expect(`length 42`).toEvaluateTo(0, globals)
-    await expect(`length true`).toEvaluateTo(0, globals)
-    await expect(`length null`).toEvaluateTo(0, globals)
+  })
+
+  test('length throws on invalid types', async () => {
+    await expect(`try: length 42 catch e: 'error' end`).toEvaluateTo('error', globals)
+    await expect(`try: length true catch e: 'error' end`).toEvaluateTo('error', globals)
+    await expect(`try: length null catch e: 'error' end`).toEvaluateTo('error', globals)
   })
 
   test('inspect formats values', async () => {
@@ -341,6 +344,84 @@ describe('collections', () => {
     await expect(`list.index-of [1 2 3] 5`).toEvaluateTo(-1, globals)
   })
 
+  test('list.push adds to end and mutates array', async () => {
+    await expect(`arr = [1 2]; list.push arr 3; arr`).toEvaluateTo([1, 2, 3], globals)
+  })
+
+  test('list.push returns the size of the array', async () => {
+    await expect(`arr = [1 2]; arr | list.push 3`).toEvaluateTo(3, globals)
+  })
+
+  test('list.pop removes from end and mutates array', async () => {
+    await expect(`arr = [1 2 3]; list.pop arr; arr`).toEvaluateTo([1, 2], globals)
+  })
+
+  test('list.pop returns removed element', async () => {
+    await expect(`list.pop [1 2 3]`).toEvaluateTo(3, globals)
+  })
+
+  test('list.pop returns null for empty array', async () => {
+    await expect(`list.pop []`).toEvaluateTo(null, globals)
+  })
+
+  test('list.shift removes from start and mutates array', async () => {
+    await expect(`arr = [1 2 3]; list.shift arr; arr`).toEvaluateTo([2, 3], globals)
+  })
+
+  test('list.shift returns removed element', async () => {
+    await expect(`list.shift [1 2 3]`).toEvaluateTo(1, globals)
+  })
+
+  test('list.shift returns null for empty array', async () => {
+    await expect(`list.shift []`).toEvaluateTo(null, globals)
+  })
+
+  test('list.unshift adds to start and mutates array', async () => {
+    await expect(`arr = [2 3]; list.unshift arr 1; arr`).toEvaluateTo([1, 2, 3], globals)
+  })
+
+  test('list.unshift returns the length of the array', async () => {
+    await expect(`arr = [2 3]; arr | list.unshift 1`).toEvaluateTo(3, globals)
+  })
+
+  test('list.splice removes elements and mutates array', async () => {
+    await expect(`arr = [1 2 3 4 5]; list.splice arr 1 2; arr`).toEvaluateTo([1, 4, 5], globals)
+  })
+
+  test('list.splice returns removed elements', async () => {
+    await expect(`list.splice [1 2 3 4 5] 1 2`).toEvaluateTo([2, 3], globals)
+  })
+
+  test('list.splice from start', async () => {
+    await expect(`list.splice [1 2 3 4 5] 0 2`).toEvaluateTo([1, 2], globals)
+  })
+
+  test('list.splice to end', async () => {
+    await expect(`arr = [1 2 3 4 5]; list.splice arr 3 2; arr`).toEvaluateTo([1, 2, 3], globals)
+  })
+
+  test('list.sort with no callback sorts ascending', async () => {
+    await expect(`list.sort [3 1 4 1 5] null`).toEvaluateTo([1, 1, 3, 4, 5], globals)
+  })
+
+  test('list.sort with callback sorts using comparator', async () => {
+    await expect(`
+      desc = do a b:
+        b - a
+      end
+      list.sort [3 1 4 1 5] desc
+    `).toEvaluateTo([5, 4, 3, 1, 1], globals)
+  })
+
+  test('list.sort with callback for strings by length', async () => {
+    await expect(`
+      by-length = do a b:
+        (length a) - (length b)
+      end
+      list.sort ['cat' 'a' 'dog' 'elephant'] by-length
+    `).toEvaluateTo(['a', 'cat', 'dog', 'elephant'], globals)
+  })
+
   test('list.any? checks if any element matches', async () => {
     await expect(`
       gt-three = do x: x > 3 end