When Larry decided that Perl 6 would incorporate concepts from prototype-based objects, he did so at least in part because it's more intuitive for people to work with, e.g., "a cow" than it is to try to work with "the concept of a cow" as a thing unto itself. In a similar way, I think that Perl's dominant concurrency system ought to be of a type that people who aren't computer scientists can grok, at least well enough to do something useful without first having to delve into the arcane depths of computing theory.
As such, I'm wondering if an Actor-based concurrency model might be a better way to go than the current threads-based mindset. Certainly, it's often easier to think of actors who talk to each other to get things done than it is to think of processes (or threads) as things unto themselves.  http://en.wikipedia.org/wiki/Actor_model -- Jonathan "Dataweaver" Lang