Routes and RegEx

I've got a question about routes. My controller has an index function that is used for showing a list of items, and some other functions for creating, editing and deleting items.

The url mysite/manage_products triggers the index function.
Now, on the list of items, I've got buttons for multiple categories, let's say: All, New and Used Products.

In my routes.php I have:

PHP Code:

$route['manage_products/all'] = 'manage_products/index/all';
$route['manage_products/new'] = 'manage_products/index/new';
$route['manage_products/used'] = 'manage_products/index/used'; 


How can I shorten this to one route?
The url manage_products/create should NOT trigger the index function, so I can't have:

PHP Code:

$route['manage_products/(:any)'] = 'manage_products/index/$1';