# Convert HoH into a list of arrayrefs: [value, key1, key2, ...]
my @list;
while (my($k1,$v1) = each(%HoH))
{
  while (my($k2,$v2) = each(%$v1))
  {
    push @list, [$v2, $k1, $k2];
  }
}

# Sort the list by its first element
@list = sort { $a->[0] <=> $b->[0] } @list;

# Now print the list
foreach my $elt (@list)
{
  print "@$elt\n";
}