Hash<...>* demonstration<...>(... a)
   Hash<...>* hash_ptr = new Hash<...>("demo_data", a);
   return new Hash<...>(
      "demonstration_data", hash_ptr
   );
}

##</code><code>##

sub demonstration {
   my %demonstration_data = ( demo_data => shift );
   return {
      demonstration_data => \%demonstration_data,
   };
}

##</code><code>##

Hash<...>* demonstration<...>(... a)
   Hash<...> hash("demo_data", a);
   return new Hash<...>(
      "demonstration_data", \hash    XXX BUG
   );
}