parser_combinator_dsl

https://github.com/moddx/parser-combinator

This library provides a DSL which you can use to easily generate parsers in Ruby. At it's core, it's a parser combinator library, but you don't need to worry about that. You build more complex expression based on simple ones, and match any formal language you want. Originally by Federico Ramirez (https://github.com/gosukiwi)