Variations on a Scheme

Come up with variations of your favorite toy problems.  The more satori the better.

I'll start with a mostly kawaii (cute) one:

(defun sepples (mosiacpointeroverflow)
  (reduce #'* (loop for grunner from 1 to mosiacpointeroverflow collect grunner) :initial-value 1))

>>6
While non-lispy syntax doesn't suit my tastes as much, I'm curious, is the code that installs that reader macro publicly available?