Regular Expressions -- for math teachers

Many people seem to be using RegEx as a way to create the variations for answers in math questions in their online courses. I've heard it's simple to learn and use, but I don't do math so I don't use RegEx. However, I have a couple of reference sites for you to check out, below.

• Regular expression checker
• Henk's regex checker (Henk is an online colleague of mine, and a real expert with regex)
  
• Regular Expression Basics: "Because there can be varying implementations, this article will cover basic principles that are commonly used."
• The Regex Coach: A free graphical application for Linux and Windows which can be used to experiment with (Perl-compatible) regular expressions interactively.
  
• Demo of RegEx for short-answer questions: Maybe you'll want to read this whole discussion thread, not just this message. Later in the thread, Henk (see item above) expands on this message's info.
  
• RegEx jumpstart for WebCT users: This thread will answer your questions and provide you with a jump start to using regular expressions in WebCT quizzes. Then here's another thread, and after that, yet another thread. :)