Ok, the discussion is becoming pointless: you like ruby for compiler construction. Well I'd rather use a language with proper tail recursion, algebraic data types, with pattern matching as a part of it, fast, strongly typed [I beleive algebraic types with pat. matching gives roughly same possibilities as does dyn. typing, for this task], with standard or at least big industrial backing behind - such as F# or Haskell. And at the end of the day get warm feeling that my code is "green" - does not waste joules, by working fast.

I appreciate your choice, but I'd myself do differently.