my @customer = Order::customer->retrieve_all;

# region descending
for (sort {$a->region->name cmp $b->region->name } @customer) {
   print $_->region->name, ' => ', $_->name, "\n";
}

# region ascending
for (sort {$b->region->name cmp $a->region->name } @customer) {
   print $_->region->name, ' => ', $_->name, "\n";
}