Your example uses two state variables: a Char and an Int, paired up as a tuple. Below, I use one state variable of type (Char,Int) for that, as hinted by your first attempt at the translation. foo and bar will each need to take a parameter --- the reference to the state variable, due to the reference business.
testfunc = do r <- newSTRef ('x',0) foo r bar r (c,n) <- readSTRef r return n
Yeap, I could do it like this myself :) The whole problem is with passing the 'r' as a parameter, which is precisly what I'm trying to avoid. I think I already understood how to use this monad. Its pretty different from the monad state I was expecting, and as far as I can see, to be used in distinct situations. Thanks J.A.
foo r = do (c,n) <- readSTRef r writeSTRef r ('a', n+1)
bar r = do (c,n) <- readSTRef r writeSTRef r (c,n+2)
tryTestFunc = runST testfunc