#!/usr/bin/perl

my $which;  

foreach my $line (<STDIN>) {
    ($line =~ /^From:.*zgp\.org/) && do {
        $which = 'example.com';
        print "From: Don Marti <dmarti\@example.com>\n"; 
        next;
    };

    ($line =~ /^From:.*example.com/) && do {
        $which = 'zgp.org';
        print "From: Don Marti <dmarti\@zgp.org>\n";
        next;
    };

    ($line eq "-- \n") && do {
        print $line;
        if ($which eq 'zgp.org') {
            print `cat ~/.signature`;
        }
        else {
            print `cat ~/.signature-example`;
        }
        exit 0;
    };

    # else
    do {
        print $line;
        next;
    };
}