0 0 0
1 0 0
2 0 0
3 0 0
0 1 0
0 2 0
0 3 0
0 0 1
1 0 1
2 0 1
3 0 1
0 1 1
0 2 1
(etc)

##</code><code>##

my @odometer = (0, 0, 0);

##</code><code>##

while_odometer_has_not_run_to_completion... {
  $id2++;
  (
    $data{$id}{$id2}{'key1'},
    $data{$id}{$id2}{'key2'},
    $data{$id}{$id2}{'key3'}, 
  )
    = 
  (
    $hash{$id}{'key1'}[ $odometer[0] ],
    $hash{$id}{'key2'}[ $odometer[1] ],
    $hash{$id}{'key3'}[ $odometer[2] ],
  );
  next_odometer( \@odometer );
}