recode8(m1, m2, str)
        Map8* m1
        Map8* m2
        PREINIT:
            STRLEN len;
            STRLEN rlen;
            char*  res;
        INPUT:
            char* str = SvPV(ST(2), len);
        CODE:
            RETVAL = newSV(len + 1);
            SvPOK_on(RETVAL);
            res = SvPVX(RETVAL);
            map8_recode8(m1, m2, str, res, len, &rlen);
            res[rlen] = '\0';
            SvCUR_set(RETVAL, rlen);
        OUTPUT:
            RETVAL