Interactive regex builder learn tool for Mac OS X? [closed]

Anyone want to recommend a good regex tool (Interactive GUI for constructing and learning) for regex syntax on Mac OS X?

What is RegEx tester?

Regex Tester is a tool to learn, build, & test Regular Expressions (RegEx / RegExp). Results update in real-time as you type. Roll over a match or expression for details. Save & share expressions with others. Explore the Library for help & examples.

How do I validate a RegEx?

To validate a field with a Regex pattern, click the Must match pattern check box. Next, add the expression you want to validate against. Then add the message your users will see if the validation fails. You can save time for your users by including formatting instructions or examples in the question description.

I can recommend Patterns, found on Mac App Store: http://itunes.apple.com/us/app/patterns-the-regex-app/id429449079?mt=12

http://rubular.com. It's on the Internet, so you should be able to use it on OS X. It uses Ruby's regexp engine, but that is similar enough to Perl and other regexp engines.