TYPEMAP
int128_t        T_INT128
uint128_t       T_UINT128

INPUT
T_INT128
        $var = SvI128(aTHX_ $arg);

T_UINT128
        $var = SvU128(aTHX_ $arg);

OUTPUT
T_INT128
        $arg = newSVi128($var);

T_UINT128
        $arg = newSVu128($var);