Static Route / predefined variables

I am trying to setup a route that sets a fixed parameter

PHP Code:

$routes->get('/', 'Pages::showme/first');
$routes->get('pages/showme/(:alphanum)', 'Pages::showme/$1'); 


hitting "/" results in

Code:

Controller method is not found: showme\first

But "/pages/showme/first" works as expected

I have read the route manual but have not found a way to do it, any help is greatly appreciated

Route code

PHP Code:

$routes->get('/', 'Pages::showme'); 


Controller method code

PHP Code:

public function showme($param = 'first') 


Default parameter value is ok, 

Thanks for your reply! That works as expected with a small caveat

Code:

/pages/showme/

is now accessible instead of throwing an error

My controller looks something like this, ie. i don't want to have a default value

PHP Code:

public function showme($param = '') {
    if($param == ''){show_404();}
.
.
.