Route regular expression should not match according to regexpal.com, but it does anyway

[eluser]hal10001[/eluser]

Code:

^([a-zA-Z-]+/)*[a-zA-Z-]+/?$

That should match the following:

category-name/sub-category-name/sub-sub-category-name/page-name

However, it should NOT match:

category-name/sub-category-name//sub-sub-category-name/page-name

Notice the double slash. The route is as follows:

Code:

$route['^([a-zA-Z-]+/)*[a-zA-Z-]+/?$'] = "homepage";

Right now I'm just redirecting to the homepage for testing purposes. When it doesn't match, it should throw a 404. So on a URL with a double slash it should be throwing a 404.