RegEx Knife

RegEx Knife is an easy and useful tool for working with Regular Expressions.  RegEx Knife is unique in how it allows you to highlight capture groups within a Regular Expression, edit them and immediately see the results. RegEx Knife also makes it easy to experiment with regular expression substitutions. Version 2 retains the simplicity of the original RegEx Knife, with the added advantage that it works on your iPhone as well as your iPad.