If the aim is to have a hyphen in the URL, I would suggest that you remove the hyphen in the folder:
/fuel/app/classes/controller/DirWithdash/Home.php
Update the routes file to the following, where home
points to your controller, and index
is your action:
'dir-withdash/(.*)' => 'DirWithdash/Home/index/$1',
And update your class to the following:
class Controller_DirWithdash_Home extends \Controller
{
public function action_index()
{
}// action_index
}