Laravel 4 Language Prefixing based on: https://gist.github.com/dhayab/6172253, http://forums.laravel.io/viewtopic.php?id=7458

app.php

/*
|--------------------------------------------------------------------------
| Languages
|--------------------------------------------------------------------------
|
| List all valid languages
*/

'languages' => array('en', 'de'),

filters.php

App::before(function($request)
{
    // locale is set and valid ?
    if ( in_array(Request::segment(1), Config::get('app.languages')) ) {
        // set locale in session and continue
        Session::put('locale', Request::segment(1));
    } else {
        // add locale and redirect
        return Redirect::to(Config::get('app.locale') . '/' . trim(Request::path(), '/'));
    }
    
    // set app locale to session locale
    if ( Session::has('locale') ) {
        App::setLocale(Session::get('locale'));
    }
});

routes.php

// get locale from request
$locale = Request::segment(1);

// prefix routes with current $locale
Route::group(['prefix' => $locale], function()
{
  // language prefixed routes
});