A low-tech concurrent interface to the console. When multiple threads want input, they send messages to the console with the format

 <thread-id>:request

The user supplies input to any requesting thread in a similar way:

 <thread-id>:response

At any time, the user can enter !! to obtain a listing of all the active prompts. Any input not of either of these forms is discarded.

example :: IO ()
example = setupStdinout processes

processes :: IO ()
processes = do
    forkIO $ (prompt "Enter something" >> return ())
    forkIO $ (prompt "Something else" >> return ())
    prompt "quit"      -- When the main thread dies,
    return ()          -- the whole interaction ends