HV* get_hidden_hash(SV* perl_obj) {
	SV* underlying_hash;
	MAGIC* mg;
	HV* hidden_hash;
	
	// get the underlying hash that the perl_obj is a reference to
	// (we can leave it an SV* because we're just using it to find magic)
	underlying_hash = SvRV(perl_obj);
	
	// get the hidden hash linked to the perl_obj
	mg = mg_find(underlying_hash, PERL_MAGIC_ext);
	hidden_hash = (HV*)mg->mg_obj;
	
	return hidden_hash;
}