Regular expressions can be difficult and every language seems to have them implemented slightly different. The basics are the same and they are explained in the LabVIEW help. For more info you can try the Regular Expressions Cookbook or any of the 20700 Google matches for "perl compatible regular expressions cheat sheet". And when you have finally mastered them, you can achieve anything!
There's one thing I'd like to show that possibly not everyone knows. Rather than cascading matches and using the "whole match" terminal, you can extend the Match Regular Expression node to get access to submatches like this: