route.js

/**
 * Simple Expressjs application demonstrating difference in routing behavior
 * between version 4.12.4 and 4.13.1.
 */
var express = require('express');
var request = require('request');
var http_server = express()
  .get('/:foo\\(:bar?\\)', function(req, res, next) {
    res.end(JSON.stringify({ 'foo': req.params.foo, 'bar': req.params.bar }));
  }).listen(8080, function() {
    request('http://localhost:8080/hello(world)', function(err, res, body) {
      // 4.12.4: {"foo":"hello","bar":"world"}
      // 4.13.1: {"foo":"hello"}
      console.log(body);
      process.exit();
    });
  });

This was confirmed as a regression in express 4.13.1, and fixed for 4.13.2