The robots waiting on the nest will see what was delivered and resume computation. In other words, a subroutine or procedure call in ToonTalk is just a very special pattern of use of trucks, birds, and robots. ToonTalk only provides the programmer with the more general ability to express the spawning of new processes. The lack of subroutines in ToonTalk makes it much more feasible to have much larger number of processes than conventional programming languages. The reason for this is that everyone implements subroutine calls using a data structure called a stack.
Stacks are a very effective way of implementing procedural calls, including recursive calls.
This makes processes somewhat costly. In contrast, when I used Java, it stopped working when I had just a few hundred processes. Conventional languages have shared state . Sharing state is necessary in these languages in order for threads to work together. This sharing between concurrent independent processes is very dangerous, however.