What part(s) of the code is incompatible with CGI.pm?

All of it, or none of it. Since it doesn't use CGI.pm, it's not "incompatible". {grin}

Perhaps your real question is "what would that script look like if it had been written using CGI.pm rather than Yet Another Broken Handrolled Parser?" In that case, the answer is, "totally different". There are more things wrong with that script than right. For example, for the right string in the email parameter, I could execute an arbitrary command on that box.

-- Randal L. Schwartz, Perl hacker