RegExplorer for Mac

From Mark Nutter:

Build syntactically-correct regular expressions using easy menu-driven commands or by typing in directly, and test at the push of a button. No more write/compile/load-search-text/repeat. Use RegExplorer to learn regular expression syntax or to develop and debug complex regular expressions for use in REALbasic or other PCRE-compatible regular expression languages and scripting systems. Supports search-and-replace, batch mode, and numbered subexpressions, and shows you exactly what matched and what didn't, so you can fine tune your regex.