code: function createWriteHead (prevWriteHead, listener) {
    var fired = false
  
    // return function with core name and argument list
    return function writeHead (statusCode) {
      // set headers from arguments
      var args = setWriteHeadHeaders.apply(this, arguments)
  
      // fire listener
      if (!fired) {
        fired = true
        listener.call(this)
  
        // pass-along an updated status code
        if (typeof args[0] === 'number' && this.statusCode !== args[0]) {
          args[0] = this.statusCode
          args.length = 1
        }
      }
  
      return prevWriteHead.apply(this, args)
    }
  }
docs: Create a replacement writeHead method.
  
  @param {function} prevWriteHead
  @param {function} listener
  @private