karlgoethebier and Anonymous Monk shows what is probably the best answer (using URI::URLand pop). The regular expression grabbing digits at the end is also reasonable, but with a fair number of caveats, many of which are on this thread.

My first instict (assuming the URL is generally consistent) would be to  splitthe URL on its slashes and popthe last entry off the result. To be fair, that would be because I wasn't familiar with URI::URLuntil I read about it on this thread.  :-)

Good luck; and please, next time, show us what you've tried on the original post, okay?