my @db;
 $db[$monthNumber]->{ProductName}{RegionName} = $Quantity;

 # Loop through Month..
 for (0..11){ #Cycle through Months, assuming zero-based
    next unless my %prod = %{$db[$_]}; # Any data there ?
   print "Some MONTH $_ header here\n";  
  foreach (sort keys %prod){
       my %region = %{$prod{$_}};
        # $region{RegionName} now has the qty to be printed
        # Hopefully, you get the idea now...
    }

 }