val threshold: Int = 10

def main(args: Array[String]) {
  _execute(_main())
}

def script..

  demultiplex =
    var window: Int = 0
    var counter: Int = 0
    (
      while (counter < 3) {
        =><1>s1: Int
        {window += s1; counter++}
        if (window > threshold) {
          =><2>s2: Int
          {window -= s2}
        }
      }
      <=window
      window  = 0
      counter = 0
      ...
    )

  stream1 = <=20 ...
  stream2 = <=30 ...

  result = dataflowCommunicationScope {
    stream1 =<1>=> demultiplex
    stream2 =<2>=> demultiplex
  }

  main = result ==> (=>x: Int; {println(x)})