T_dbtkeydatum_btree
        {
            SV* my_sv = $arg ;
            DBM_ckFilter(my_sv, filter_store_key, \"filter_store_key\");
            DBT_clear($var) ;
            SvGETMAGIC($arg) ;
            if (db->recno_or_queue ||
                    (db->type == DB_BTREE && flagSet(DB_SET_RECNO))) {
                Value = GetRecnoKey(db, SvIV(my_sv)) ;
                $var.data = & Value;
                $var.size = (int)sizeof(db_recno_t);
            }
            else {
            STRLEN len;
                $var.data = SvPV(my_sv, len);
                $var.size = (int)len;
            }
        }