/prog/'s own esoteric language

Fun idea. Let's make our own programming language.
Conditions:
Must be somewhat useful like ABC.
Not limited to characters only. Can include words.
1 function per post.

>>88
Ew, extra paren after x.upper, sorry. No parens matching in browser.

Another example:

(for x (xrange 1 11)
  (for y (xrange 1 11)
    (print (% '%4d' (* x y)))))

As you can see, filthy statements are turned into beautiful expressions.