The Regulator is described as 'advanced Regular expressions testing tool, featuring syntax highlighting and web-service integration with Regexlib.coms database of online regular expressions'. There are more than 25 alternatives to The Regulator for a variety of platforms, including Windows, Online / Web-based, Mac, Self-Hosted solutions and Linux. The best alternative is RegExr, which is both free and Open Source. Other great apps like The Regulator are regular expressions 101 (Free), Expresso (Free), RegexBuddy (Paid) and iHateRegex (Free, Open Source).
The award-winning Expresso editor is equally suitable as a teaching tool for the beginning user of regular expressions or as a full-featured development environment for the experienced programmer or web designer with an extensive knowledge of regular expressions.