RLisp - Lisp naturally embedded in Ruby

I just wrote a Lisp interpretter embedded in Ruby. I used ANTLR 3.0ea7 for parsing (it's alpha-quality software, unfortunately).

$ cat examples/fib.rl
(defun fib (n)
(if (<= n 1)
  1
  (+ (fib (- n 1)) (fib (- n 2)))
 )
)
(map fib '(1 2 3 4 5))
$ ./rlisp.rb <examples/fib.rl
#<lambda:0 ...>
(1 2 3 5 8) 

The dialect is supposed to be vaguely based on Scheme, but the idea was for it to be naturally embedded in Ruby, so many thing had to be changed compared to Scheme:

• send function for method calls: (send 2 '+ 2) and syntactic sugar for it [obj method arguments], which evaluates to (obj 'method arguments). So it's possible to write [2 + [3 * 4]], what expands to (send 2 '+ (send 3 '* 4)). The syntax was stolen from Objective C.
• lists are implemented as arrays. So no cons, car or cdr. Now of course we need some replacement, and I haven't really thought about it. You can send get/set method to Array object, like that ('(a b c) set 0 'd) (or ['(a b c) get 0]).

Things that would be required before RLisp is usable (even as a funky toy):

• macro system - doh, that's the point of the whole thing
• links to Ruby object system, so we can define classes, methods etc.
• some support for iterators, I have no idea what syntax to select for iterators (send-with-iterator '(1 2 3) 'each (lambda (i) (print i))) would probably do the trick, but it's kinda uglyish.
• support for other basic Ruby objects like hash tables, regular expressions etc. Most of them need little more than (let a (send Hash 'new)), but some might not be very usable in such form.
• exception handling and callcc support would be cool

Oh, and it uses dynamic binding like Emacs Lisp instead of lexical like Scheme/Common Lisp, because it was much easier to do ;-). It should probably be fixed later. My box on which the code repository is located is behind a nasty nat, so just mail me if you want the code. :-)