It's a shame parsers are such a PITA to write. So many problems could be trivially solved if writing a grammar and generating a parser for it were in any way a pleasant process.
I've found Parsing Expression Grammars (PEGs) great for that sort of task. Way nicer than kludging something with regexes anyway, and way more powerful.
There's a Lua library called LPeg [1], which introduces a DSL of a kind to Lua that lets you write PEGs with minimal effort. The vis editor [2] uses LPeg files as lexers for syntax highlighting, and they look very clean IMO; for example, this is the C lexer: https://github.com/martanne/vis/blob/master/lua/lexers/ansi_...