code: String next() {
          while (true) {
              nextToken();
              if (sval != null && !isQuoted() && sval.startsWith("-")) {
                  // allow POSIX getopt() option format,
                  // to be consistent with command-line
                  String opt = sval.startsWith("--")
                          ? sval.substring(1)
                          : sval;
                  foundOption(opt);
              } else {
                  break;
              }
          }
          return sval;
      }
docs: Return the next non-option argument. Encountered options are stored.
  
  @return the token string, or null if there are no more tokens