How PHPBB checks if you're allowed to access an ACP module...

gistfile1.php

<?php
function module_auth($module_auth, $forum_id = false)
{
    // ...
    $is_auth = false;
    eval('$is_auth = (int) (' . preg_replace(array('#acl_([a-z0-9_]+)(,\$id)?#', '#\$id#', '#aclf_([a-z0-9_]+)#', '#cfg_([a-z0-9_]+)#', '#request_([a-zA-Z0-9_]+)#'), array('(int) $auth->acl_get(\'\\1\'\\2)', '(int) $forum_id', '(int) $auth->acl_getf_global(\'\\1\')', '(int) $config[\'\\1\']', '!empty($_REQUEST[\'\\1\'])'), $module_auth) . ');');
    // AAAAAAAAAAAAAAAAAAAAAAAHHH!
    // ...
}