Edit: for the unfamiliar, http://ed-thelen.org/comp-hist/APL-hist.html .
Edit: and for the other side: http://en.wikipedia.org/wiki/Criticism_of_the_APL_programmin...
Here's what I did. For a set of problems, of increasing difficulty, I would write a solution procedure, using the notation of A Programming Language I would then ask the graduate student assigned to me to:
program the procedure in any programming language he chose,
execute the procedure for a representative set of data values
give me his program and answers so that I could compare them with the specifications I had written and the answers I had previously calculated.
The result, which I still find surprising and impressive, was: In every case, what was programmed was exactly what I specified.