I have been working with regular expressions quite a bit over the last few weeks, and have had numerous occasions when the regex I’m writing doesn’t do what I want it to do.
I would consider myself somewhere between beginner and intermediate when it comes to regexes. I know how to do most simple things, and I understand why a lot of fairly complex regexes are written the way they are. However, when it comes to actually writing complex regexes, I usually find myself forgetting something really simple, or banging my head against the wall over and over again because I can’t figure out the one character I need to add or take out of it.
However, I’ve now found a great resource to help me when I get stuck. The Regular Expression Library is a site completely devoted to regexes. The site has a huge database of user-contributed regexes, along with a cheat sheet, a tester (albeit a tester that only allows you to test javascript or vb.net regexes), a list of other good resources and forums for the discussion of regexes. It really seems to be a one-stop-shop for regular expressions.