diff --git a/bootstrap.php b/bootstrap.php
index 33cb8d4..0090745 100644
--- a/bootstrap.php
+++ b/bootstrap.php
@@ -1,16 +1,17 @@
 <?php
 require('vendor/autoload.php');
 
-function ml_get_lisp(): array
+function ml_get_lisp(bool $debug): array
 {
     $tokenizer = new MadLisp\Tokenizer();
     $reader = new MadLisp\Reader();
     $printer = new MadLisp\Printer();
     $eval = new MadLisp\Evaller($tokenizer, $reader, $printer);
+    $eval->setDebug($debug);
 
     $lisp = new MadLisp\Lisp($tokenizer, $reader, $eval, $printer);
 
-    // Environment
+    // Root environment
     $env = new MadLisp\Env('root');
 
     // Register core functions
@@ -25,5 +26,8 @@ function ml_get_lisp(): array
     (new MadLisp\Lib\Time())->register($env);
     (new MadLisp\Lib\Types())->register($env);
 
+    // User environment
+    $env = new MadLisp\Env('user', $env);
+
     return [$lisp, $env];
 }
diff --git a/run.php b/run.php
index 7d7655f..1b27934 100644
--- a/run.php
+++ b/run.php
@@ -1,32 +1,60 @@
 <?php
 require('bootstrap.php');
 
-list($lisp, $rootEnv) = ml_get_lisp();
-
-// Read history
-$historyFile = $_SERVER['HOME'] . '/.madlisp_history';
-if (is_readable($historyFile)) {
-    readline_read_history($historyFile);
+if (php_sapi_name() != 'cli') {
+    exit('Currently only cli usage is supported.');
 }
 
-// Create new env for user definitions
-$userEnv = new MadLisp\Env('repl', $rootEnv);
-
-while (true) {
-    $input = readline('> ');
-
-    try {
-        $lisp->rep($input, $userEnv);
-
-        if ($input) {
-            readline_add_history($input);
-            readline_write_history($historyFile);
-        }
-    } catch (MadLisp\MadLispException $ex) {
-        print('error: ' . $ex->getMessage());
-    } catch (TypeError $ex) {
-        print('error: invalid argument type: ' . $ex->getMessage());
+function ml_repl($lisp, $env)
+{
+    // Read history
+    $historyFile = $_SERVER['HOME'] . '/.madlisp_history';
+    if (is_readable($historyFile)) {
+        readline_read_history($historyFile);
     }
 
-    print(PHP_EOL);
+    while (true) {
+        $input = readline('> ');
+
+        try {
+            $lisp->rep($input, $env);
+
+            if ($input) {
+                readline_add_history($input);
+                readline_write_history($historyFile);
+            }
+        } catch (MadLisp\MadLispException $ex) {
+            print('error: ' . $ex->getMessage());
+        } catch (TypeError $ex) {
+            print('error: invalid argument type: ' . $ex->getMessage());
+        }
+
+        print(PHP_EOL);
+    }
 }
+
+function ml_run()
+{
+    $args = getopt('de:f:r');
+
+    $debug = array_key_exists('d', $args);
+
+    list($lisp, $env) = ml_get_lisp($debug);
+
+    if (array_key_exists('e', $args)) {
+        $lisp->rep($args['e'], $env);
+    } elseif (array_key_exists('f', $args)) {
+        $input = "(load \"{$args['f']}\")";
+        $lisp->rep($input, $env);
+    } elseif (array_key_exists('r', $args)) {
+        ml_repl($lisp, $env);
+    } else {
+        print("Usage:" . PHP_EOL);
+        print("-d         :: Debug mode" . PHP_EOL);
+        print("-e <code>  :: Evaluate code" . PHP_EOL);
+        print("-f <file>  :: Evaluate file" . PHP_EOL);
+        print("-r         :: Run the interactive repl" . PHP_EOL);
+    }
+}
+
+ml_run();
diff --git a/src/Evaller.php b/src/Evaller.php
index 8bd130f..bc10bfe 100644
--- a/src/Evaller.php
+++ b/src/Evaller.php
@@ -7,7 +7,7 @@ class Evaller
     protected Reader $reader;
     protected Printer $printer;
 
-    private const DEBUG = true;
+    protected bool $debug = false;
 
     public function __construct(Tokenizer $tokenizer, Reader $reader, Printer $printer)
     {
@@ -18,7 +18,7 @@ class Evaller
 
     public function eval($ast, Env $env)
     {
-        if (self::DEBUG) {
+        if ($this->debug) {
             print("eval: ");
             $this->printer->print($ast);
             print("\n");
@@ -27,7 +27,7 @@ class Evaller
 
         while (true) {
 
-            if (self::DEBUG) {
+            if ($this->debug) {
                 if ($loops++ > 0) {
                     print("eval loop: ");
                     $this->printer->print($ast);
@@ -257,6 +257,11 @@ class Evaller
         }
     }
 
+    public function setDebug(bool $val): void
+    {
+        $this->debug = $val;
+    }
+
     private function evalAst($ast, Env $env)
     {
         if ($ast instanceof Symbol) {