# Pastebin O07cRtXO
>>> program = """
...     (define fact
...             ;; Factorial function
...             (lambda (n)
...                     (if (eq n 0)
...                             1 ; Factorial of 0 is 1, and we deny
...                             ; the existence of negative numbers
...                             (* n (fact (- n 1))))))
... """
>>> parse(program)
['define', 'fact', ['lambda', ['n'], ['if', ['eq', 'n', '0'], 1, ['*', 'n', ['fact', ['-', 'n', 1]]]]]]