} else if (con.match != null && refno < 0) {
                      int index = -refno;
                      int save = con.match.getEnd(index);
                      con.match.setEnd(index, offset);
                      int ret = this. matchString (con, op.next, offset, dx, opts);
                      if (ret < 0)  con.match.setEnd(index, save);
                      return ret;
                  }