RegExr is an online tool for editing and testing Regular Expressions (RegExp / RegEx). It provides a simple interface to enter RegEx expressions, and visualize matches in real-time editable source text. It also provides a handy RegExp snippet sidebar with descriptions and usage examples to make it easier to learn Regular Expressions through trial and error.
RegExr is built with Flex 3, and uses ActionScript 3's built in RegExp engine. RegExr uses an extension of the TextHilighter class that comes with the Spelling Plus Library.
http://gskinner.com/RegExr/
