True. But nowadays most regex implementations are quite good (apparently go's is not - I haven't used it). That said, most regex performance problems are PEBKA

True. But nowadays most regex implementations are quite good (apparently go's is not - I haven't used it). That said, most regex performance problems are PEBKAC. Writing a fast regex is hard and requires a pretty thorough understanding of parser theory. And many who use regexes don't understand that it's critical to precompile them for performance. You don't get a fast parser when you rebuild the DFA each time you use it. *edit: a word