You'll also want to investigate Prolog. That's the grandfather of pattern-matching tree-manipulation languages. Also, it is dynamically typed if that floats y

You'll also want to investigate Prolog. That's the grandfather of pattern-matching tree-manipulation languages. Also, it is dynamically typed if that floats your boat more than Haskell or ML. ML always forces you to deal with incomplete patterns, but you need to specifically ask your Haskell compiler to warn you about incomplete patterns. It is hard to beat Prolog for quickly whipping up prototype language interpreters. Besides pattern matching, there are easy to use symbols (just start a word with a lower case letter), declarative semantics, definite clause grammars (for parsing), user definable infix, prefix, and postfix operators, etc