diff --git a/luash b/luash
index 6a61184..77f6b3d 100755
--- a/luash
+++ b/luash
@@ -1,21 +1,33 @@
 #!/usr/bin/env lua
 -- luash: Minimal Lua shell scripting preprocessor
 
--- Load injected library into global scope for REPL
+-- Module path for local src/
+package.path = (debug.getinfo(1, "S").source:match("@(.*/)") or "./") .. "src/?.lua;" .. package.path
+
+-- Load injected library via module
 local function load_injected_lib()
-  local injected_lib_path = debug.getinfo(1, "S").source:match("@(.*/)") or "./"
-  local lib_file = io.open(injected_lib_path .. "__injected_lib.lua", "r")
-  if lib_file then
-      local lib_code = lib_file:read("*a")
-      lib_file:close()
-      local lib_func = load(lib_code)
-      if lib_func then lib_func() end
-  end
+  local injected = require('injected')
+  injected.load()
 end
 
 -- REPL (Interactive Shell) Implementation
 function start_repl()
   load_injected_lib()
+  local repl_mod = require('repl')
+  
+  -- Preprocessing functions (simplified versions for REPL)
+  local function process_env_vars_repl(code)
+    local pre = require('preprocess')
+    return pre.process_env_vars(code)
+  end
+  local function process_shell_commands_repl(code)
+    local pre = require('preprocess')
+    return pre.process_shell_commands(code)
+  end
+  local function process_interactive_commands_repl(code)
+    local pre = require('preprocess')
+    return pre.process_interactive_commands(code)
+  end
 
   -- Preprocessing functions (simplified versions for REPL)
   local function process_env_vars_repl(code)
@@ -133,12 +145,8 @@ function start_repl()
 
   -- Luash preprocessing function for REPL
   local function preprocess_luash_repl(code)
-      -- Remove shebang line if present and preserve line numbers
-      local has_shebang = code:match("^#!")
-      code = code:gsub("^#![^\r\n]*[\r\n]?", "")
-      if has_shebang then
-        code = "\n" .. code
-      end
+      local pre = require('preprocess')
+      code = pre.remove_shebang_preserve_lines(code)
       code = process_env_vars_repl(code)
       code = process_interactive_commands_repl(code)
       code = process_shell_commands_repl(code)
@@ -210,218 +218,8 @@ function start_repl()
       return s:match("^%s*(.-)%s*$")
   end
 
-  -- Raw mode (optional) for immediate key handling like Ctrl+L
-  local function detect_tty()
-      local r = os.execute("test -t 0 >/dev/null 2>&1")
-      if type(r) == "number" then return r == 0 end
-      return r == true
-  end
-  local env_raw = os.getenv("LUASH_RAW")
-  local raw_mode_enabled = (env_raw == "1") or (env_raw == nil and detect_tty())
-
-  local function set_raw_mode(enable)
-      if enable then
-          os.execute("stty -echo -icanon -isig min 1 time 0")
-      else
-          os.execute("stty sane")
-      end
-  end
-
-  local function raw_read_line(prompt)
-      io.write(prompt)
-      io.flush()
-      local buf = {}
-      while true do
-          local ch = io.read(1)
-          if not ch then
-              return nil
-          end
-          local b = string.byte(ch)
-          if b == 10 or b == 13 then -- Enter
-              io.write("\n")
-              return table.concat(buf)
-          elseif b == 12 then -- Ctrl+L
-              -- Clear screen and reprint banner + prompt + current buffer
-              repl.buffer = table.concat(buf)
-              io.write("\27[2J\27[H")
-              io.flush()
-              print("🚀 Luash Interactive Shell")
-              print("Type Lua expressions, use $VAR for env vars, `commands` for shell")
-              print("Special commands: .help .exit .clear .history  (Ctrl+L to clear, Ctrl+D to exit)")
-              print("")
-              io.write(prompt)
-              io.write(repl.buffer)
-              io.flush()
-              -- Keep current input for usability, but allow immediate Ctrl+D by not forcing buf non-empty
-              -- buf remains as-is
-          elseif b == 3 then -- Ctrl+C
-              return "__CTRL_C__"
-          elseif b == 4 then -- Ctrl+D
-              -- Exit immediately (treat as EOF) regardless of current buffer state
-              return nil
-          elseif b == 127 or b == 8 then -- Backspace/Delete
-              if #buf > 0 then
-                  table.remove(buf)
-                  io.write("\b \b")
-                  io.flush()
-              end
-          else
-              table.insert(buf, ch)
-              io.write(ch)
-              io.flush()
-          end
-      end
-  end
-
-  -- Main REPL loop
-  print("🚀 Luash Interactive Shell")
-  print("Type Lua expressions, use $VAR for env vars, `commands` for shell")
-  print("Special commands: .help .exit .clear .history  (Ctrl+L to clear, Ctrl+D to exit)")
-  print("")
-  
-  if raw_mode_enabled then set_raw_mode(true) end
-  local ok_loop, loop_err = pcall(function()
-  while true do
-      local prompt = repl.buffer == "" and "luash> " or "    >> "
-      local line
-      if raw_mode_enabled then
-          line = raw_read_line(prompt)
-          if line == "__CTRL_C__" then
-              print("\nInterrupted (Ctrl+C)")
-              break
-          end
-      else
-          io.write(prompt)
-          io.flush()
-          -- Safely read a line; handle Ctrl+C gracefully
-          local ok, l = pcall(io.read, "*line")
-          if not ok then
-              print("\nInterrupted (Ctrl+C)")
-              break
-          end
-          line = l
-      end
-      
-      if not line then -- EOF (Ctrl+D)
-          print("\nGoodbye!")
-          break
-      end
-      
-      -- Handle Ctrl+L (form feed) to clear screen in non-raw mode
-      if (not raw_mode_enabled) and line:find(string.char(12), 1, true) then
-          repl.buffer = ""
-          io.write("\27[2J\27[H") -- Clear screen and move cursor to top
-          io.flush()
-          print("🚀 Luash Interactive Shell")
-          print("Type Lua expressions, use $VAR for env vars, `commands` for shell")
-          print("Special commands: .help .exit .clear .history  (Ctrl+L to clear, Ctrl+D to exit)")
-          print("")
-          goto continue
-      end
-
-      line = trim(line)
-      
-      -- Handle special dot commands
-      if line == ".exit" or line == ".quit" then
-          break
-      elseif line == ".clear" then
-          repl.buffer = ""
-          print("Buffer cleared")
-      elseif line == ".history" then
-          for i, cmd in ipairs(repl.history) do
-              print(string.format("%3d: %s", i, cmd))
-          end
-      elseif line == ".help" then
-          print([[
-Luash Interactive Shell Help:
-
-Luash Features:
-  $VAR              - Access environment variables
-  $VAR = "value"    - Set environment variables
-  `command`         - Execute shell commands
-  #{var}            - Variable interpolation in commands
-  !command          - Interactive shell commands
-
-Special Commands:
-  .help             - Show this help
-  .exit, .quit      - Exit the shell
-  .clear            - Clear input buffer
-  .history          - Show command history
-
-Examples:
-  print("Hello " .. $USER)
-  files = `ls -la`
-  $GREETING = "Hello World"
-  result = `echo #{$GREETING}`
-  !ps aux | head -5
-
-Multi-line input supported for functions, loops, etc.]])
-      else
-          -- Add to buffer
-          if repl.buffer ~= "" then
-              repl.buffer = repl.buffer .. "\n" .. line
-          else
-              repl.buffer = line
-          end
-          
-          -- Try to compile to determine if we need continuation (parser-driven)
-          if line ~= "" then
-              local processed = preprocess_luash_repl(repl.buffer)
-              
-              -- First, try as an expression (so results print automatically)
-              local func, err = load("return " .. processed, "@repl")
-              if not func then
-                  if err and err:match("<eof>") then
-                      -- Incomplete chunk; wait for more input
-                      -- keep buffer as-is
-                  else
-                      -- Try as a statement block
-                      func, err = load(processed, "@repl")
-                      if not func then
-                          if err and err:match("<eof>") then
-                              -- Incomplete; wait for more input
-                          else
-                              -- Definitive syntax error; report and clear buffer
-                              print("Syntax error: " .. err)
-                              repl.buffer = ""
-                          end
-                      else
-                          -- Executable statement block
-                          table.insert(repl.history, repl.buffer)
-                          local success, result = pcall(func)
-                          if success then
-                              if result ~= nil then
-                                  print(tostring(result))
-                              end
-                          else
-                              print("Error: " .. tostring(result))
-                          end
-                          repl.buffer = ""
-                      end
-                  end
-              else
-                  -- Executable expression
-                  table.insert(repl.history, repl.buffer)
-                  local success, result = pcall(func)
-                  if success then
-                      if result ~= nil then
-                          print(tostring(result))
-                      end
-                  else
-                      print("Error: " .. tostring(result))
-                  end
-                  repl.buffer = ""
-              end
-          end
-      end
-      ::continue::
-  end
-  end)
-  if raw_mode_enabled then set_raw_mode(false) end
-  if not ok_loop then
-      if raw_mode_enabled then set_raw_mode(false) end
-      print("\nREPL error: " .. tostring(loop_err))
-  end
+  -- Delegate to module REPL
+  repl_mod.start(preprocess_luash_repl, load_injected_lib)
 end
 
 -- 1. Check for an input file or REPL mode
@@ -436,201 +234,7 @@ elseif not filename or filename == "-i" or filename == "--interactive" then
   start_repl()
   return
 end
-
-local file = io.open(filename, "r")
-if not file then
-  print("Error: Cannot open file '" .. filename .. "'")
-  return
-end
-local source_code = file:read("*a")
-file:close()
-
--- Remove shebang line if present and preserve line numbers
-local has_shebang = source_code:match("^#!")
-source_code = source_code:gsub("^#![^\r\n]*[\r\n]?", "")
-
--- If we removed a shebang, add an empty line to preserve line numbers
-if has_shebang then
-  source_code = "\n" .. source_code
-end
-
-
-
--- Preprocessing functions
-local function process_env_vars(code)
-local lines = {}
-  for line in code:gmatch("([^\r\n]*)") do
-    if not line:match("^%s*%-%-") then -- Skip comments
-      
-      -- Handle environment variable assignment: $VAR=value
-      if line:match("^%$([%w_]+)%s*=") then
-        line = line:gsub("^%$([%w_]+)%s*=%s*(.+)", function(var, value)
-          return "env_set('" .. var .. "', " .. value .. ")"
-        end)
-      else
-        -- Handle $VAR substitution, but not inside strings
-        local in_string = false
-        local quote_char = nil
-        local result = ""
-        local i = 1
-        
-        while i <= #line do
-          local char = line:sub(i, i)
-          
-          -- Track string boundaries
-          if (char == '"' or char == "'") and (i == 1 or line:sub(i-1, i-1) ~= "\\") then
-            if not in_string then
-              in_string = true
-              quote_char = char
-            elseif char == quote_char then
-              in_string = false
-              quote_char = nil
-            end
-            result = result .. char
-            i = i + 1
-          elseif char == "$" and not in_string then
-            -- Found $ outside of string, check for variable pattern
-            local var_match = line:sub(i):match("^%$([%w_]+)")
-            if var_match then
-              result = result .. "env_get('" .. var_match .. "')"
-              i = i + #var_match + 1
-            else
-              result = result .. char
-              i = i + 1
-            end
-          else
-            result = result .. char
-            i = i + 1
-          end
-        end
-        
-        line = result
-      end
-    end
-    table.insert(lines, line)
-  end
-  
-  return table.concat(lines, "\n")
-end
-
-local function process_shell_commands(code)
-  local lines = {}
-  for line in code:gmatch("([^\r\n]*)") do
-    -- Skip processing backticks inside strings
-    local in_string = false
-    local quote_char = nil
-    local result = ""
-    local i = 1
-    
-    while i <= #line do
-      local char = line:sub(i, i)
-      
-      -- Track string boundaries
-      if (char == '"' or char == "'") and (i == 1 or line:sub(i-1, i-1) ~= "\\") then
-        if not in_string then
-          in_string = true
-          quote_char = char
-        elseif char == quote_char then
-          in_string = false
-          quote_char = nil
-        end
-        result = result .. char
-        i = i + 1
-      elseif char == "`" and not in_string then
-        -- Found backtick outside of string, find the closing backtick
-        local end_pos = line:find("`", i + 1)
-        if end_pos then
-          local command = line:sub(i + 1, end_pos - 1)
-          
-          -- Handle variable interpolation with #{var} syntax
-          if command:find("#{") then
-            -- Escape existing quotes first, then do interpolation
-            local escaped_cmd = command:gsub('"', '\\"')
-            local interpolated_cmd = escaped_cmd:gsub("#{([%w_.]+)}", '" .. tostring(%1) .. "')
-            result = result .. 'shell("' .. interpolated_cmd .. '")'
-          else
-            result = result .. 'shell("' .. command:gsub('"', '\\"') .. '")'
-          end
-          i = end_pos + 1
-        else
-          result = result .. char
-          i = i + 1
-        end
-      else
-        result = result .. char
-        i = i + 1
-      end
-    end
-    
-    table.insert(lines, result)
-  end
-  
-  return table.concat(lines, "\n")
-end
-
-local function process_interactive_commands(code)
-  local lines = {}
-  for line in code:gmatch("([^\r\n]*)") do
-    -- Only match ! at the beginning of the line (ignoring whitespace)
-    local command = line:match("^%s*!(.*)")
-    if command then
-      local indent = line:match("^(%s*)")
-      table.insert(lines, indent .. 'run("' .. command:gsub('"', '\\"') .. '")')
-    else
-      table.insert(lines, line)
-    end
-  end
-  return table.concat(lines, "\n")
-end
-
--- Load injected helper functions (minimal)
-local injected_lib_path = debug.getinfo(1, "S").source:match("@(.*/)") or "./"
-local lib_file = io.open(injected_lib_path .. "__injected_lib.lua", "r")
-local injected_lib = ""
-if lib_file then
-  injected_lib = lib_file:read("*a")
-  lib_file:close()
-end
-
--- Apply preprocessing
-source_code = process_env_vars(source_code)
-source_code = process_interactive_commands(source_code)
-source_code = process_shell_commands(source_code)
-
--- Debug output
-if os.getenv("LUASH_DEBUG") then
-  print("-- Generated Lua code:")
-  print(source_code)
-  print("-- End generated code")
-end
-
--- Pre-load injected library into global environment
-if injected_lib ~= "" then
-  local lib_func, lib_err = load(injected_lib, "@__injected_lib.lua")
-  if lib_func then
-    local success, result = pcall(lib_func)
-    if not success then
-      print("--- ERROR loading injected library ---")
-      print(result)
-      return
-    end
-  else
-    print("--- SYNTAX ERROR in __injected_lib.lua ---")
-    print(lib_err)
-    return
-  end
-end
-
--- Execute the user's source code (with correct line numbers)
-local func, err = load(source_code, "@" .. filename)
-if not func then
-  print("--- SYNTAX ERROR in " .. filename .. " ---")
-  print(err)
-else
-  local success, result = pcall(func)
-  if not success then
-    print("--- RUNTIME ERROR in " .. filename .. " ---")
-    print(result)
-  end
-end
+-- Delegate to runner for file execution
+local runner = require('runner')
+runner.run_file(filename)
 
diff --git a/src/injected.lua b/src/injected.lua
new file mode 100644
index 0000000..1604965
--- /dev/null
+++ b/src/injected.lua
@@ -0,0 +1,24 @@
+local M = {}
+
+function M.load()
+  local base = debug.getinfo(1, "S").source:match("@(.*/)") or "./"
+  base = base:gsub("/src/?$", "/")
+  local lib_file = io.open(base .. "src/lib/injected_lib.lua", "r")
+  if lib_file then
+      local lib_code = lib_file:read("*a")
+      lib_file:close()
+      local lib_func, err = load(lib_code, "@__injected_lib.lua")
+      if lib_func then
+        local ok, res = pcall(lib_func)
+        if not ok then
+          error("Error loading injected lib: " .. tostring(res))
+        end
+      else
+        error("Syntax error in injected lib: " .. tostring(err))
+      end
+  end
+end
+
+return M
+
+
diff --git a/__injected_lib.lua b/src/lib/injected_lib.lua
similarity index 100%
rename from __injected_lib.lua
rename to src/lib/injected_lib.lua
diff --git a/src/main.lua b/src/main.lua
new file mode 100644
index 0000000..64d92d0
--- /dev/null
+++ b/src/main.lua
@@ -0,0 +1,35 @@
+local runner = require('runner')
+
+local M = {}
+
+function M.run(argv)
+  local filename = argv[1]
+  if filename == "-h" or filename == "--help" then
+    print("Usage: luash <script.luash>")
+    print("       luash -i  # Interactive mode")
+    print("       luash -h  # Show this help")
+    return
+  elseif not filename or filename == "-i" or filename == "--interactive" then
+    local entry = require('repl')
+    local preprocess = require('preprocess')
+    local injected = require('injected')
+    local function preprocess_luash_repl(code)
+      code = preprocess.remove_shebang_preserve_lines(code)
+      code = preprocess.process_env_vars(code)
+      code = preprocess.process_interactive_commands(code)
+      code = preprocess.process_shell_commands(code)
+      return code
+    end
+    local function load_injected_lib()
+      injected.load()
+    end
+    entry.start(preprocess_luash_repl, load_injected_lib)
+    return
+  else
+    runner.run_file(filename)
+  end
+end
+
+return M
+
+
diff --git a/src/preprocess.lua b/src/preprocess.lua
new file mode 100644
index 0000000..e98521a
--- /dev/null
+++ b/src/preprocess.lua
@@ -0,0 +1,120 @@
+local M = {}
+
+function M.remove_shebang_preserve_lines(source_code)
+  local has_shebang = source_code:match("^#!")
+  source_code = source_code:gsub("^#![^\r\n]*[\r\n]?", "")
+  if has_shebang then
+    source_code = "\n" .. source_code
+  end
+  return source_code
+end
+
+function M.process_env_vars(code)
+  local lines = {}
+  for line in code:gmatch("([^\r\n]*)") do
+    if not line:match("^%s*%-%-") then
+      if line:match("^%$([%w_]+)%s*=") then
+        line = line:gsub("^%$([%w_]+)%s*=%s*(.+)", function(var, value)
+          return "env_set('" .. var .. "', " .. value .. ")"
+        end)
+      else
+        local in_string = false
+        local quote_char = nil
+        local result = ""
+        local i = 1
+        while i <= #line do
+          local char = line:sub(i, i)
+          if (char == '"' or char == "'") and (i == 1 or line:sub(i-1, i-1) ~= "\\") then
+            if not in_string then
+              in_string = true
+              quote_char = char
+            elseif char == quote_char then
+              in_string = false
+              quote_char = nil
+            end
+            result = result .. char
+            i = i + 1
+          elseif char == "$" and not in_string then
+            local var_match = line:sub(i):match("^%$([%w_]+)")
+            if var_match then
+              result = result .. "env_get('" .. var_match .. "')"
+              i = i + #var_match + 1
+            else
+              result = result .. char
+              i = i + 1
+            end
+          else
+            result = result .. char
+            i = i + 1
+          end
+        end
+        line = result
+      end
+    end
+    table.insert(lines, line)
+  end
+  return table.concat(lines, "\n")
+end
+
+function M.process_interactive_commands(code)
+  local lines = {}
+  for line in code:gmatch("([^\r\n]*)") do
+    local command = line:match("^%s*!(.*)")
+    if command then
+      local indent = line:match("^(%s*)")
+      table.insert(lines, indent .. 'run("' .. command:gsub('"', '\\"') .. '")')
+    else
+      table.insert(lines, line)
+    end
+  end
+  return table.concat(lines, "\n")
+end
+
+function M.process_shell_commands(code)
+  local lines = {}
+  for line in code:gmatch("([^\r\n]*)") do
+    local in_string = false
+    local quote_char = nil
+    local result = ""
+    local i = 1
+    while i <= #line do
+      local char = line:sub(i, i)
+      if (char == '"' or char == "'") and (i == 1 or line:sub(i-1, i-1) ~= "\\") then
+        if not in_string then
+          in_string = true
+          quote_char = char
+        elseif char == quote_char then
+          in_string = false
+          quote_char = nil
+        end
+        result = result .. char
+        i = i + 1
+      elseif char == "`" and not in_string then
+        local end_pos = line:find("`", i + 1)
+        if end_pos then
+          local command = line:sub(i + 1, end_pos - 1)
+          if command:find("#{") then
+            local escaped_cmd = command:gsub('"', '\\"')
+            local interpolated_cmd = escaped_cmd:gsub("#{([%w_.]+)}", '" .. tostring(%1) .. "')
+            result = result .. 'shell("' .. interpolated_cmd .. '")'
+          else
+            result = result .. 'shell("' .. command:gsub('"', '\\"') .. '")'
+          end
+          i = end_pos + 1
+        else
+          result = result .. char
+          i = i + 1
+        end
+      else
+        result = result .. char
+        i = i + 1
+      end
+    end
+    table.insert(lines, result)
+  end
+  return table.concat(lines, "\n")
+end
+
+return M
+
+
diff --git a/src/repl.lua b/src/repl.lua
new file mode 100644
index 0000000..410a977
--- /dev/null
+++ b/src/repl.lua
@@ -0,0 +1,130 @@
+local M = {}
+
+function M.start(preprocess_fn, load_injected_lib)
+  load_injected_lib()
+
+local util = require('util')
+local function detect_tty() return util.is_tty() end
+  local env_raw = os.getenv("LUASH_RAW")
+  local raw_mode_enabled = (env_raw == "1") or (env_raw == nil and detect_tty())
+
+  local repl = { buffer = "", history = {}, history_index = 0 }
+
+  local function set_raw_mode(enable) util.set_raw_mode(enable) end
+
+  local function trim(s) return util.trim(s) end
+
+  local function raw_read_line(prompt)
+      io.write(prompt); io.flush()
+      local buf = {}
+      while true do
+          local ch = io.read(1)
+          if not ch then return nil end
+          local b = string.byte(ch)
+          if b == 10 or b == 13 then io.write("\n"); return table.concat(buf)
+          elseif b == 12 then -- Ctrl+L
+              repl.buffer = table.concat(buf)
+              io.write("\27[2J\27[H"); io.flush()
+              print("🚀 Luash Interactive Shell")
+              print("Type Lua expressions, use $VAR for env vars, `commands` for shell")
+              print("Special commands: .help .exit .clear .history  (Ctrl+L to clear, Ctrl+D to exit)")
+              print("")
+              io.write(prompt); io.write(repl.buffer); io.flush()
+          elseif b == 3 then return "__CTRL_C__"
+          elseif b == 4 then return nil -- Ctrl+D as EOF
+          elseif b == 127 or b == 8 then if #buf > 0 then table.remove(buf); io.write("\b \b"); io.flush() end
+          else table.insert(buf, ch); io.write(ch); io.flush() end
+      end
+  end
+
+  print("🚀 Luash Interactive Shell")
+  print("Type Lua expressions, use $VAR for env vars, `commands` for shell")
+  print("Special commands: .help .exit .clear .history  (Ctrl+L to clear, Ctrl+D to exit)")
+  print("")
+
+  if raw_mode_enabled then set_raw_mode(true) end
+  local ok_loop, loop_err = pcall(function()
+    while true do
+      local prompt = repl.buffer == "" and "luash> " or "    >> "
+      local line
+      if raw_mode_enabled then
+        line = raw_read_line(prompt)
+        if line == "__CTRL_C__" then print("\nInterrupted (Ctrl+C)"); break end
+      else
+        io.write(prompt); io.flush()
+        local ok, l = pcall(io.read, "*line")
+        if not ok then print("\nInterrupted (Ctrl+C)"); break end
+        line = l
+      end
+      if not line then print("\nGoodbye!"); break end
+
+      if (not raw_mode_enabled) and line:find(string.char(12), 1, true) then
+        repl.buffer = ""; io.write("\27[2J\27[H"); io.flush()
+        print("🚀 Luash Interactive Shell")
+        print("Type Lua expressions, use $VAR for env vars, `commands` for shell")
+        print("Special commands: .help .exit .clear .history  (Ctrl+L to clear, Ctrl+D to exit)")
+        print(""); goto continue
+      end
+
+      line = trim(line)
+      if line == ".exit" or line == ".quit" then break
+      elseif line == ".clear" then repl.buffer = ""; print("Buffer cleared")
+      elseif line == ".history" then for i, cmd in ipairs(repl.history) do print(string.format("%3d: %s", i, cmd)) end
+      elseif line == ".help" then print([[Luash Interactive Shell Help:
+
+Luash Features:
+  $VAR              - Access environment variables
+  $VAR = "value"    - Set environment variables
+  `command`         - Execute shell commands
+  #{var}            - Variable interpolation in commands
+  !command          - Interactive shell commands
+
+Special Commands:
+  .help             - Show this help
+  .exit, .quit      - Exit the shell
+  .clear            - Clear input buffer
+  .history          - Show command history
+
+Multi-line input supported for functions, loops, etc.]])
+      else
+        if repl.buffer ~= "" then repl.buffer = repl.buffer .. "\n" .. line else repl.buffer = line end
+
+        if line ~= "" then
+          local processed = preprocess_fn(repl.buffer)
+          local func, err = load("return " .. processed, "@repl")
+          if not func then
+            if err and err:match("<eof>") then
+              -- incomplete
+            else
+              func, err = load(processed, "@repl")
+              if not func then
+                if err and err:match("<eof>") then
+                  -- incomplete
+                else
+                  print("Syntax error: " .. err); repl.buffer = ""
+                end
+              else
+                table.insert(repl.history, repl.buffer)
+                local success, result = pcall(func)
+                if success then if result ~= nil then print(tostring(result)) end else print("Error: " .. tostring(result)) end
+                repl.buffer = ""
+              end
+            end
+          else
+            table.insert(repl.history, repl.buffer)
+            local success, result = pcall(func)
+            if success then if result ~= nil then print(tostring(result)) end else print("Error: " .. tostring(result)) end
+            repl.buffer = ""
+          end
+        end
+      end
+      ::continue::
+    end
+  end)
+  if raw_mode_enabled then set_raw_mode(false) end
+  if not ok_loop then if raw_mode_enabled then set_raw_mode(false) end; print("\nREPL error: " .. tostring(loop_err)) end
+end
+
+return M
+
+
diff --git a/src/runner.lua b/src/runner.lua
new file mode 100644
index 0000000..7c5bfa9
--- /dev/null
+++ b/src/runner.lua
@@ -0,0 +1,39 @@
+local preprocess = require('preprocess')
+local injected = require('injected')
+
+local M = {}
+
+function M.run_file(filename)
+  local file = io.open(filename, "r")
+  if not file then
+    print("Error: Cannot open file '" .. filename .. "'")
+    return
+  end
+  local source_code = file:read("*a")
+  file:close()
+
+  source_code = preprocess.remove_shebang_preserve_lines(source_code)
+  source_code = preprocess.process_env_vars(source_code)
+  source_code = preprocess.process_interactive_commands(source_code)
+  source_code = preprocess.process_shell_commands(source_code)
+
+  -- Load injected helpers into global scope (not prepended to source)
+  injected.load()
+
+  -- Execute
+  local func, err = load(source_code, "@" .. filename)
+  if not func then
+    print("--- SYNTAX ERROR in " .. filename .. " ---")
+    print(err)
+    return
+  end
+  local success, result = pcall(func)
+  if not success then
+    print("--- RUNTIME ERROR in " .. filename .. " ---")
+    print(result)
+  end
+end
+
+return M
+
+
diff --git a/src/util.lua b/src/util.lua
new file mode 100644
index 0000000..8edceb4
--- /dev/null
+++ b/src/util.lua
@@ -0,0 +1,27 @@
+local M = {}
+
+function M.trim(s)
+  return s:match("^%s*(.-)%s*$")
+end
+
+function M.is_tty()
+  local r = os.execute("test -t 0 >/dev/null 2>&1")
+  if type(r) == "number" then return r == 0 end
+  return r == true
+end
+
+function M.set_raw_mode(enable)
+  if enable then
+    os.execute("stty -echo -icanon -isig min 1 time 0")
+  else
+    os.execute("stty sane")
+  end
+end
+
+function M.script_dir()
+  return (debug.getinfo(2, "S").source:match("@(.*/)") or "./")
+end
+
+return M
+
+