And they shall call it "LISP" :)

Really, run through the first chapter of SICP, which shows how each step of a LISP computation (well, Scheme technically) is performed until you get the basic answer. One could build an interpreter that takes a basic LISP expression (you don't need a full LISP, just the basic arithmatic operations are enough), and then show the reduction of each step until you get the final answer.

You'll have to live with prefix-notation instead of the common infix notation, but I think we need more of that, anyway.