MVar in Haskell Concurrent

conc.hs

import Control.Concurrent
import Control.Concurrent.MVar
import Control.Monad.Fix (fix)

--seg:: MVar Int -> MVar Int -> Int -> IO ()
seg mself mnext n loop = do
    mn <- takeMVar mself
    putStrLn $ show mn
    putMVar mnext n
    loop
    
main = do
    let ls = [0..9]
    mselfs@(m0:mx) <- sequence [newEmptyMVar| _ <- ls]
    let mnexts = mx ++ [m0]
    let fs = [forkIO $ fix $ seg mself mnext $ (n + 1) `mod` 10| (mself, mnext, n) <- zip3 mselfs mnexts ls]
    sequence_ fs
    
    putStrLn "Main Thread."
    let print029 = do
        putMVar m0 0
        takeMVar m0

    print029
    return ()