}
      last = idx[0];
      last = interp.relToAbsIndex(s.length, last);
    }
    if (first > 0) {
      head = s.substring(0, first);
    }
    mid = s.substring(first, last+1).toUpperCase();
    if (last+1 < s.length) {
      tail = s.substring(last+1);
    }
    s = head+mid+tail;
    interp.setResultString(s);
    return interp.OK;
  });

  /* ==================== command string trim ===================================== */