mdict-parser.js
function spreadus() {
    var args = Array.prototype.slice.apply(arguments);
    args._spreadus_ = true;
    return args;
  }
function spreadus() {
    var args = Array.prototype.slice.apply(arguments);
    args._spreadus_ = true;
    return args;
  }
For sliceThen(..).exec(proc, ..), mark what proc function returns is multiple values
to be passed to further Promise#spread(..) call.