I was a little surprised he took until the final paragraph to mention
Racket. If he had played around with it then I think the article might
have read differently.
" Racket is a Lisp dialect that’s specifically designed for creating
new languages (a technique sometimes referred to as
language-oriented programming). I haven’t had time to play around
much with Racket myself, but it looks like a very suitable tool for
creating 'little languages'."