Using is preferable to spawn() for asynchronous calls in some cases since it's quite wasteful to create and set up an anonymous function that does nothing but call a proc.

However, waitfor is poorly documented and may be deprecated.
What's the situation on that?

Also, in terms the language, how tough would it be to implement an async call keyword? Seems as simple as replacing the following proc call with null and adding a new instance of the called proc to the top of the scheduler after the current one.