Expiring page caches with regexp?

Is there a way to expire page caches using regular expressions like
you can with fragment caches?

I'm writing an app which has a catalogue style product listing but not
full on e-commerce. It's pretty simple; with just categories and
products within them. A url for a product called "Band Saws" within
the category "Heavy duty saws" would look like "http://domain.com/
products/heavy-duty-saws/band-saws".

The problem is that when an admin user edits a category ("Heavy duty
saws"), I need to expire the entire "heavy-duty-saws" directory in
public to wipe every product which has been cached within that
category. With fragment caching, I'd just use regexp, but that doesn't
seem to work in page caching (at least the same way it does with
fragments).

I tried using "system "rm -rf #{RAILS_ROOT}/public/products/
#{category.url_slug}" from within the CategorySweeper which I was
trying to get the expire_page method to work in but it didn't work
either (I didn't really dig far into why this one wasn't working..
should it?)

Thanks in advance for any help.