pepperspray, regular expressions allow you to look through text for specific patterns. So, the guy swinging in from above knows how to write a regular expression to identify text that looks like an address, presumably the vacation address for the girl.
Lots of languages use regex, but Perl has a pretty powerful regex library, hence the reason he's typing in Perl. There's a certain geek affection for the language too, even though a lot of people (like me) don't like it.
When you have to explain it, it's not as funny.