URL Routing: With or without trailing slash

[eluser]jonnyjon[/eluser]
Hi,
I have a route set up:

$route['directory/(:any)'] = "controller/function/$1";

The problem is that...
This works: http://example.com/directory/whatever
But this doesn't work: http://example.com/directory

I know I could add a second route:
$route['directory'] = "controller/function";

But is there a way to incorporate a reg ex to handle both cases in one statement?

This this (but this doesn't work):
$route['directory[\/*](:any)'] = "controller/function/$1";