[1 of 1] Compiling Main             ( /in/foo.hs, /tmp/Main.o )

/in/foo.hs:7:32: error:
    * Couldn't match type `()' with `IO b'
      Expected type: [()] -> IO b
        Actual type: [()] -> ()
    * In the second argument of `(>>=)', namely `return ()'
      In the expression: forM p3 print >>= return ()
      In the expression:
        let
          p1 = primesBounded n
          p2 = dropWhile (< m) p1
          p3 = filter isPalindromic p2
        in forM p3 print >>= return ()
    * Relevant bindings include
        main :: IO (IO b) (bound at /in/foo.hs:3:1)