TYPEMAP
HV *		T_HvRV

OUTPUT
T_HvRV
	$arg = newRV((SV*)$var);

INPUT
T_HvRV
	if( SvROK($arg) && (SvTYPE(SvRV($arg)) == SVt_PVHV) )
		$var = (HV*)SvRV( $arg );
	else {
		warn( \"${Package}::$func_name() -- $var is not an HV reference\" );
		XSRETURN_UNDEF;
	}
