I have found http://www.regular-expressions.info/quickstart.html very helpful working with regex's. Lots of good examples.
Also whats happening when you get an uninitialized value error is that part of your regular expression is not working and returning blank results within the (). Also I found tools like http://www.txt2re.com/ or Eclipses regex tool to be helpful in debugging my regex commands.
-- Grey Fox
"We are grey. We stand between the darkness and the light" B5

In reply to Re: New to Regex and need help by Grey Fox
in thread New to Regex and need help by MKevin

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