The error/issue usually arises when you trigger Tainting on the top (shebang) line (#!/usr/bin/perl -wT), but are running the program/script via the perl interpreter on the command line (as you mention above).

If you do, Perl sees that you want to use Tainting from the first line, but because of the way you called it, it can't. So add -T to the command line call, as well:

perl -cT  price.cgi

See if that doesn't help.