my (%old, %new);
...
for my $printer (sort keys %old) {
 print("Printer $printer not in new\n"),
  next unless exists $new{$printer};
 for my $name (sort keys %{$old{$printer}}) {
  print("Attribute $name not in new for printer $printer\n"),
   next unless exists $new{$printer}{$name};
  for my $val (sort keys %{$old{$printer}{$name}}) {
   print("Val $val not in new for printer $printer attrib $name\n"),
    next unless exists $new{$printer}{$name}{$val};
  }
 }
}

# Then do the reverse comparision looping over %new
# I'm sure you can figure that out