@resources = {cdrw0 cdrw1 cdrw2}
my $chld;
while (@thisround) {
    my @sort_resource = sort(@resource);
    @resource = @sort_resource;
    while (@resource) {
        last unless @thisround;
        my $resource = shift @resource;
        my $data = shift @thisround;

        if (($chld = fork()) > 0) {
           # parent code
           # % jobs holds pid -> resource
           $jobs{$chld} = $resource;
        } else {
           # child code
           runcmd($resource, $data);
           exit;           # end chld, trigger $SIG{CHLD}
        }
    }

    sleep until @resource == $num_resources;
    last unless @thisround;
}
sleep until keys %jobs == 0;    # wait for all jobs