Script to filter by header (by Marc Mutz)
This perl script can be used with a pipe through filter action after a "remove header Reply-To" action. It's useful for people who want to change certain headers based on the content of other headers...This particular script [as written right now] replaces (if used in conjunction with the remove header Reply-To action) the Reply-To header of mails sent from a debian-style bugtracking system with @bugs.kde.org. This is useful if bug reports are delivered to developers through a mailinglist that overwrites the Reply-To header with its post address:

#!/usr/bin/perl
    $endOfHeader = 0;
    while (<>) {
        if ( $endOfHeader == 0 )
        {
            if ( /^(?i:Subject):\s+Bug\#(\d{4,5}):/ )
            {
                $_ = "Reply-To: $1\@bugs.kde.org\n".$_;
            }
            elsif ( /^$/ )
            {
                $endOfHeader = 1;
            }
        }
        print;
    };