diff --git a/bootstrap.php b/bootstrap.php
deleted file mode 100644
index 0090745..0000000
--- a/bootstrap.php
+++ /dev/null
@@ -1,33 +0,0 @@
-<?php
-require('vendor/autoload.php');
-
-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);
-
-    // Root environment
-    $env = new MadLisp\Env('root');
-
-    // Register core functions
-    $lisp->register($env);
-
-    // Register libraries
-    (new MadLisp\Lib\Collections())->register($env);
-    (new MadLisp\Lib\Compare())->register($env);
-    (new MadLisp\Lib\IO())->register($env);
-    (new MadLisp\Lib\Math())->register($env);
-    (new MadLisp\Lib\Strings())->register($env);
-    (new MadLisp\Lib\Time())->register($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 e2c8fe8..5639bdd 100644
--- a/run.php
+++ b/run.php
@@ -1,11 +1,11 @@
 <?php
-require('bootstrap.php');
+require(__DIR__ . '/vendor/autoload.php');
 
 if (php_sapi_name() != 'cli') {
     exit('Currently only cli usage is supported.');
 }
 
-function ml_repl($lisp, $env)
+function ml_repl($lisp)
 {
     // Read history
     $historyFile = $_SERVER['HOME'] . '/.madlisp_history';
@@ -17,7 +17,7 @@ function ml_repl($lisp, $env)
         $input = readline('> ');
 
         try {
-            $lisp->rep($input, $env, true);
+            $lisp->rep($input, true);
 
             if ($input) {
                 readline_add_history($input);
@@ -37,17 +37,16 @@ function ml_run()
 {
     $args = getopt('de:f:r');
 
-    $debug = array_key_exists('d', $args);
-
-    list($lisp, $env) = ml_get_lisp($debug);
+    $factory = new MadLisp\LispFactory();
+    $lisp = $factory->make();
 
     if (array_key_exists('e', $args)) {
-        $lisp->rep($args['e'], $env, false);
+        $lisp->rep($args['e'], false);
     } elseif (array_key_exists('f', $args)) {
         $input = "(load \"{$args['f']}\")";
-        $lisp->rep($input, $env, false);
+        $lisp->rep($input, false);
     } elseif (array_key_exists('r', $args)) {
-        ml_repl($lisp, $env);
+        ml_repl($lisp);
     } else {
         print("Usage:" . PHP_EOL);
         print("-d         :: Debug mode" . PHP_EOL);
diff --git a/src/Lisp.php b/src/Lisp.php
index 6ede8ed..2e3d559 100644
--- a/src/Lisp.php
+++ b/src/Lisp.php
@@ -7,53 +7,25 @@ class Lisp
     protected Reader $reader;
     protected Evaller $eval;
     protected Printer $printer;
+    protected Env $env;
 
-    public function __construct(Tokenizer $tokenizer, Reader $reader, Evaller $eval, Printer $printer)
+    public function __construct(Tokenizer $tokenizer, Reader $reader, Evaller $eval, Printer $printer, Env $env)
     {
         $this->tokenizer = $tokenizer;
         $this->reader = $reader;
         $this->eval = $eval;
         $this->printer = $printer;
+        $this->env = $env;
     }
 
-    public function rep(string $input, Env $env, bool $printReadable): void
+    public function rep(string $input, bool $printReadable): void
     {
         $tokens = $this->tokenizer->tokenize($input);
 
         $expr = $this->reader->read($tokens);
 
-        $result = $this->eval->eval($expr, $env);
+        $result = $this->eval->eval($expr, $this->env);
 
         $this->printer->print($result, $printReadable);
     }
-
-    public function register(Env $env): void
-    {
-        $env->set('doc', new CoreFunc('doc', 'Get documentation for a function.', 1, 1,
-            function ($a) {
-                if ($a instanceof Func) {
-                    return $a->getDoc();
-                }
-
-                throw new MadLispException('first argument to doc is not function');
-            }
-        ));
-
-        $env->set('read', new CoreFunc('read', 'Read string as code.', 1, 1,
-            fn (string $a) => $this->reader->read($this->tokenizer->tokenize($a))
-        ));
-
-        $env->set('print', new CoreFunc('print', 'Print argument. Give second argument as true to show strings in readable format.', 1, 2,
-            function ($a, bool $readable = false) {
-                $this->printer->print($a, $readable);
-                return null;
-            }
-        ));
-
-        $env->set('error', new CoreFunc('error', 'Throw an exception using argument (string) as message.', 1, 1,
-            function (string $error) {
-                throw new MadLispException($error);
-            }
-        ));
-    }
 }
diff --git a/src/LispFactory.php b/src/LispFactory.php
new file mode 100644
index 0000000..ad0a2fd
--- /dev/null
+++ b/src/LispFactory.php
@@ -0,0 +1,63 @@
+<?php
+namespace MadLisp;
+
+class LispFactory
+{
+    public function make(array $libraries = []): Lisp
+    {
+        $tokenizer = new Tokenizer();
+        $reader = new Reader();
+        $printer = new Printer();
+        $eval = new Evaller($tokenizer, $reader, $printer);
+
+        // Root environment
+        $env = new Env('root');
+
+        // Register core functions
+        $env->set('doc', new CoreFunc('doc', 'Get documentation for a function.', 1, 1,
+            function ($a) {
+                if ($a instanceof Func) {
+                    return $a->getDoc();
+                }
+
+                throw new MadLispException('first argument to doc is not function');
+            }
+        ));
+
+        $env->set('read', new CoreFunc('read', 'Read string as code.', 1, 1,
+            fn (string $a) => $reader->read($tokenizer->tokenize($a))
+        ));
+
+        $env->set('print', new CoreFunc('print', 'Print argument. Give second argument as true to show strings in readable format.', 1, 2,
+            function ($a, bool $readable = false) use ($printer) {
+                $printer->print($a, $readable);
+                return null;
+            }
+        ));
+
+        $env->set('error', new CoreFunc('error', 'Throw an exception using argument (string) as message.', 1, 1,
+            function (string $error) {
+                throw new MadLispException($error);
+            }
+        ));
+
+        // Register core libraries
+        (new Lib\Collections())->register($env);
+        (new Lib\Compare())->register($env);
+        (new Lib\IO())->register($env);
+        (new Lib\Math())->register($env);
+        (new Lib\Strings())->register($env);
+        (new Lib\Time())->register($env);
+        (new Lib\Types())->register($env);
+
+        // Register additional libraries
+        foreach ($libraries as $lib) {
+            $lib->register($env);
+        }
+
+        // User environment
+        $env = new Env('user', $env);
+
+        return new Lisp($tokenizer, $reader, $eval, $printer, $env);
+    }
+}