Regex is a regular-expression testing tool that is easy to use. Features Immediate feedback. Dynamic highlighting of matches as you modify the regular expression or sample text Automatic escaping of special characters when copying a regular expression Automatic unescaping of special characters when pasting a regular expression Supports capture groups Supports matching options such as case-insensitive matches Supports positive lookahead, negative lookahead Supports positive lookbehind, negative lookbehind Supports backreferences Fast and dead-simple to use
See the regular expressions tutorial at http://motionobj.com/articles/regex-macos-tutorial.