Why not using any of the Mail::* modules? I can't remember exactly, but Mail::Sendmail or Mail::Mailer lets you specify several headers.

Update:

use Mail::Mailer;
$mailer = new Mail::Mailer;
$mailer->open(\%headers);
print $mailer $body;
$mailer->close;
[download]

So you can have your headers in the %headers hash.