{
        use Fcntl qw(:flock);
        my %h;
        my $size=5;

        sub ringopen {
                open(F, ">ring.lock") || die;
                flock(F, LOCK_EX);
                dbmopen(%h, "ring", 0666) || die;
        }
        sub ringclose { dbmclose(%h); close(F); }
        sub ringadd {
                ringopen();
                local $_=$h{next};
                delete $h{$_-$size} if (defined $_);
                $h{$h{next}++}=$_[0];
                ringclose();
        }
        sub ringdump {
                ringopen();
                my @a=sort { $a <=> $b } 
                          grep /^\d+$/, keys %h;
                @a=@h{@a};
                ringclose();
                return @a;
        }
}