Laravel Pass Parameter from Route to Filter

I am using the laravel framework. If I have the following route:

Route::get('/test/{param}', array('before'=>'test_filter', 'SomeController@anyAction'));

And this filter:

Route::filter('test_filter', function() {
    $param = [Get the parameter from the url];
    return "The value is $param";
});

How can I pass parameters to the filter so that when visiting /test/foobar I would get a page saying: "The value is foobar"?