custom_profile_router.php

<?php
Route::set('profile', '<username>', array('username' => '([a-zA-Z0-9\-_\.]+)') )
	->defaults(array(
			'controller' => 'profile',
			'action' => 'index'
		));

Route::set('default', '(<controller>(/<action>))')
        ->defaults(array(
            'controller' => 'welcome',
            'action' => 'index',
        ));

// Error
Route::set('error', 'error(/<path>)', array('path' => '.+'))
        ->defaults(array(
            'controller' => 'error',
            'action' => '404',
            'id' => FALSE,
        ));