TYPEMAP
Parrot_Interp	T_PTROBJ
PMC*	T_PTROBJ
INPUT
T_PMC
	if (sv_derived_from($arg, "PMC")) {
	    IV tmp = SvIV((SV*)SvRV($arg));
	    $var = INT2PTR($type,tmp);
	}
	else
	    Perl_croak(aTHX_ "PMC")
OUTPUT
T_PMC
	sv_setref_pv($arg, "PMC", (void*)$var);