OMeta: an Object-Oriented Language for Pattern Matching

Interesting. OMeta can create a new parser that inherits from an existing parser. It's unique. But we have to not just parse but also evaluate. OMeta's external DSL is excellent for parsing but seems difficult to use for evaluating.

There are other parser libraries based on PEG such as pyPEG (Python), LPeg (Lua) or Parsec (Haskell). They use internal DSL rather than external DSL. I have used Parslet (Ruby) in my project and it's worth to try. http://kschiess.github.com/parslet/