Re: CHECKING IF HEADER DEFINED

[Your Mother]

This is a possibility in some (sloppily/disparately coded) cases but only if you're using CGI to do your headers already.

use CGI;
$CGI::HEADERS_ONCE = 1;

(Sidebar: your user name is, of course, up to you but please change your sig block. This is not a place of worship for anything but Perl.)

[GrandFather]

This being a Perl Monastery the bible is The Camel Book so the path to Godliness being sought is surely perfection on Perl coding. Bearing that in mind the OP's sig is most apposite and to be lauded. He is obviously shouting for the sake of the pure joy in his journey. ;-)