for (1..1000) {
    print "Next number : ", xCount::next_num(), "\n";
}

package xCount;

sub next_num {
    if (open(ON, "+<seqfile")){
        flock ON, 2;
        $ordernum = <ON>;
        $ordernum += 1;
        seek ON, 0, 0;
        print ON $ordernum;
        flock ON, 8;
        close(ON);
    }
    return $ordernum;
}

1;