How do I retrieve a uri segment in a hook?

[eluser]Salvatore Formisano[/eluser]
Even this alone fails (just deleted the rest to make sure the mistake is here:

Code:

<?
function pick_language() {

  require_once(APPPATH.'/config/language.php');

  session_start();

  $x=load_class('uri')->segment(1);
  define('CURRENT_LANGUAGE', $x);
}

?>

and in case this can be useful, here's the hook declaration:

Code:

$hook['pre_system'] = array(
  'class'    => '',
  'function' => 'pick_language',
  'filename' => 'pick_language.php',
  'filepath' => 'hooks'
);