No, essentially it is so the the thread 'entry point' (the subroutine that forms the thread essentially) can have a different context than that of the create() which started the thread, that is to say you can tell it in advance what context the join() will be called in so that wantarray() will work properly, bearing in mind that the thread may already have checked wantarray to determine what to return before the context of the join is known.

/J\