I've only rolled my own when working with such a basic grammar (or such basic aspects of a grammar) that simple regex felt faster than dealing with actual parsi

I've only rolled my own when working with such a basic grammar (or such basic aspects of a grammar) that simple regex felt faster than dealing with actual parsing. That said, most of that was at a time when I was much less comfortable with lex/yacc, so maybe I'd be more keen on them now.