O erudite ones!

having used the site passively for some time,and gained a lot, I ask for your forebearance for any breaches of etiquette or displays of fundamental ignorance (easily possible) now that I have the trepidation to ask a question:

a search for my problem produced just what I wanted at How can I send an HTML error message to a user who leaves form fields blank?: Ovid's tip on CGI method display_page_with_errors, which looked really neat. Unfortunatey CGI seems to have changed in the meantime because my system doesn't recognize the method. Here's the message I get from Apache:

"Undefined subroutine &main::display_page_with_errors called at C:/.......".

A search of CPAN produces a load of fragmented methods, but nothing corresponding neatly to page_with_errors.

Is there something out there easy to use for someone of modest talents, or have I misunderstood something very basic?

In any event, many thanks in advance to anyone who looks at this....

Peter..