Oyster is described as 'Regular expressions are a powerful tool for developers, but they aren't the easiest things to build and debug. Oyster helps you interactively build and test them, storing each "pearl" in an easy to access library' and is an app in the Development category. There are more than 25 alternatives to Oyster for a variety of platforms, including Windows, Online / Web-based, Mac, Linux and Self-Hosted solutions. The best alternative is RegExr, which is both free and Open Source. Other great apps like Oyster are regular expressions 101 (Free), Expresso (Free), RegexBuddy (Paid) and PowerGREP (Paid).
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.
Quickly search through large numbers of files on your PC or network using powerful text patterns to find exactly the information you want. Search and replace with plain text or regular expressions to maintain web sites, source code, reports, ...