import scala.actors.Actor
import scala.actors.Actor._

class Stage1(val next:Actor) extends Actor {
 def act() {
  while (true) {
   receive {
    case n: Int => next ! n*n
   }
  }
 }
}

class Stage2(val next:Actor) extends Actor {
 def act() {
  while (true) {
   receive {
    case n: Int => next ! n.toString
   }
  }
 }
}

class Stage3 extends Actor {
 def act() {
  while (true) {
   receive {
    case s: String => println(s.length)
   }
  }
 }
}

Output:

scala> val s3 = new Stage3; val s2 = new Stage2(s3); val s1 = new Stage1(s2); (1 to 10) foreach { s1 ! _ }
1
1
1
2
2
2
2
2
2
3