code: function injectBefore(replServer, method, beforeFn) {
    var _orig = replServer[method];
    replServer[method] = function() {
      var args = Array.prototype.slice.call(arguments);
      var callback = args.pop();
      beforeFn.apply(null, args.concat(function(err, res) {
        if (err || res) {
          callback(err, res);
        } else {
          _orig.apply(replServer, args.concat(callback));
        }
      }));
    };
    return replServer;
  }
docs: Intercept the evaled value returned from repl evaluator, convert and send back to output.
  @private