What are some alternatives?
When comparing RegexBuddy and Expresso, you can also consider the following products
RegExr - RegExr.com is an online tool to learn, build, and test Regular Expressions.
Grammarly - Clear, effective, mistake-free writing everywhere you type.
regular expressions 101 - Extensive regex tester and debugger with highlighting for PHP, PCRE, Python and JavaScript.
Regex Hero - Online Silverlight regular expression tester with instantaneous highlighting, C# and VB.NET code generation, code completion, regex analysis, benchmarking, and more.
RegexMagic - Use RegexMagic to generate complete regular expressions to your specifications by using RegexMagic's flexible patterns, instead of the cryptic regex syntax.
Regulex - Open-source, regular expression parser and visualizer.