[racket] Use of map and eval to evaluate symbol in namespace

I can see how someone might want to do tricks like this, to use the REPL 
as user interface, for tinkering, and that could be very interesting or 
clever.

However, just to be clear to students and professionals who might 
stumble upon this thread... If I were actually doing this in production 
for pharmaceutical prescriptions/labeling/instructions, then I would be 
concerned about both program correctness and reducing potential for 
operator error to cause failures.  If we were starting with those as key 
requirements for production use, then I think some of this technical 
discussion might be irrelevant to that, since the software might be 
implemented in a very different way.

Neil V.