Writing regular expression is always tough for me, not to mention trying to read regular expressions written by other programmers. I found this excellent FREE tool: Regular Expression Designer provided by radsoftware.com.au a Sydney based company.
As you can see from the screen-shot below, it makes it very easy to experiment and visually inspect output of regular expression applied against various text input. You can try MATCH, SEARCH or REPLACE with one click. Match results are displayed in a tree format, so that you can instantly see all the matches and captured groups. An online help of regular expression language elements is provided as a quick reference.
This application only runs on Windows computer with .NET Framework 1.1 or 2.0.