Did you cheat and use a regex library in your lexer, or did you build a regex engine aswell?

I built recursive descent parser, and a lexer using the posix regex libary in 2 days first attempt and extra 14 days for semantic analysis and x86 code generation which operated by walking the ast. Most of those days were mostly learning x86 assembly. I can't understand 6 months, unless you did everything from scratch like the regex engine I.E Constructing NFA's, converting to DFA's etc etc.