for my $country_name (keys(%$countries)) {
   my $country = $countries->{$country_name};
   ...
}

##</code><code>##

for my $province_name (keys(%$provinces)) {
   my $province = $provinces->{$province_name};
   ...
}

##</code><code>##

for my $country_name (keys(%$countries)) {
   my $country = $countries->{$country_name};

   my $provinces = $country->{provinces};

   for my $province_name (keys(%$provinces)) {
      my $province = $provinces->{$province_name};
      ...
   }
}