The idea is that we all write CGI and just about every CGI
writer or Java Servlet writer, or PHP... or even ModPerl..
or...) ends up printing certain standard pieces of info to
the screen to see just what sort of data that they are receiving. 
So... we write a loop and print out our variables. 

Either have ModCGIDebug tack on the info to your CGI while it
is running or use the handy dandy .env virtual page to see all
that there is to seeor at least what we have found the need to
print out so far).

Some assembly required, batteries not included. 

WWW: http://www.tangent.org/mod_cgi_debug/