Mine

<?
global $SESS;
$languages = array("nl","en");
$changnl = false;
$changeen = false;
$curln = substr(trim($_SERVER['PHP_SELF']),strlen($_SERVER['PHP_SELF'])-4,3);

if($curln == "/en" || $curln =="/nl"){
		$aln = $curln;
}else{
		$aln = $SESS->userdata['language'];
}
switch ($aln)
{
		case "/en":
				$lang="en";
				$new_lang="english";
				$changeen = true;
				break;
		case "/nl":
				$lang = "nl";
				$new_lang = "dutch";
				$changnl = true;
				break;
		default :
				$lang="nl";
}

?>

{exp:template_language:future language="<?php echo $new_lang; ?>"}