If you're like me, debugging Regular Expressions can be a pain. There are an infinite amount of resources on the 'Net, but testing a home brew RegEx can be a pain. A little while ago I found this site that will not only guide you in making them, but help make sure that it does what you want it to validate. Over at
Kvalley Computers and Internet -- RegEx Evaluator they've got a pretty comprehensive tool to create and validate Regular Expressions. Check it out.