in reply to CGI calculator

#!/usr/bin/perl require("cgi-lib.pl"); &ReadParse(*input);

That approach was considered old hat 15 years ago - have you been reading Matt's Script Archive or similar?. I suggest you lose those perl4-isms and instead look to CPAN for eg. CGI, CGI::Lite or CGI::Simple to get you started. Don't prepend your subroutine calls with an "&" and always use strict and warnings. Now would also be an excellent time to become familiar with taint mode.