for my $mail (qw( bar@foo.com.com
                  bar@foo.computers.com
                  bar@com.computers.com
                  bar@b.com.computers.org)) {
    print "Looking at '$mail'\n";
    printf "index '.com': %d\n", index '.com', $mail;
    printf "index '.com.com': %d\n", index '.com.com', $mail;
    printf "rindex '.com': %d\n", rindex '.com', $mail;
}