5 -- This test hopefully exercises the black hole code. The main thread
6 -- forks off another thread and starts on a large computation.
7 -- The child thread attempts to get the result of the same large
8 -- computation (and should get blocked doing so, because the parent
9 -- won't have evaluated it yet). When the result is available, the
10 -- child passes it back to the parent who prints it out.
20 if test > 0 -- evaluate test
21 then do result <- takeMVar x