The only other obvious way (to me, at least) would be to flatten this into a list of [$host, $tgt, $dev, $X] tuples. HoHoH or LoL is entirely up to you.

BTW: You never state what the content of  $rez{$host}->{$tgt}->{$dev} is, so I called it $X. Anyhow, it will need to go along for the ride.

- doug