my @industrycodes = sort keys %db;
foreach $i (@industrycodes) {
   print "Suppliers in the $db{$i}{industry}:\n";
   my %s = %$db{$i}{suppliers};
   # Note that:  We wanted the hash of suppliers,
   # so we had to dereference with the hash sigil, %
   # The dereferencing of the references used for the
   # nesting is all handled automatically by the
   # subscripting syntax, so you don't have to mess
   # with it, but when you want to retrieve something
   # other than a scalar (e.g, an array or hash), 
   # you do have to dereference the retrieved result.
   foreach $supplier (sort keys %s) {
      print "\t$supplier => $s{$supplier}\n";
   }
}