You can only use php operators that take one parameter: See http://ez.no/products/ez_publish/documentation/development/kernel/custom_template_operators under limitations.
Instead you'll have to check your language in site.ini an make the url using the concat function.
Problem with hardcoded urls is that it isn't portable between different configurations. I used the ezurl() operator to automatically add the index.php(?) if needed. My development site runs on a machine with mod_php, and the production server uses CGI, so they need different urls.
