anchor.diff:  val future : Future[List[String]] =
     List("1","2","3")
       .async // start a new async task
  -    .par // run one op for each cpu
  -    .progress(1.second)(progress => println(progress)) // print progress
  -    .retry { // retry some errors
  -      // ...
  +    .throttle(3.second) // perform operations no faster than 1 every 3 seconds
  +    .retry { // retry some errors with a random delay
  +      case _:TimeoutException =>
  +        Future.delayed(Random.nextInt(100).millis)(true)
  +      case _ => false.future
       }
       .map(read) // sequence results and fail-immediately on exception (unlike Future.sequence)
   ----
  
positive.code: 
  ----
  
  Create configurable async tasks with error retry, throttle and parallel operation controls:
  [source,scala,numbered]
  ----
  // Tuple-based async task (heterogeneous)
  
negative.code: async // start a new async task
    .par(2) // run 2 ops at a time
    .progress(1.second)(progress => println(progress)) // print progress
    .retry { // retry some errors with a random delay
      case _:TimeoutException =>
        Future.delayed(Random.nextInt(100).millis)(true)
      case _ => false.future
    }
    .run(
  