Import the built-in package as follows:

import Control.Parallel.Strategies

Evaluate the expression in a tuple in parallel. We perform this task twice with different strategies to demonstrate how strategies are easily swapped to change the parallel nature of the code as follows:

main = do
  let (a, b) = withStrategy (parTuple2 rseq rseq) (task1, task2)
  print $ seq (a+b) "done 1"
  let (a, bs) = withStrategy (parTuple2 rseq rdeepseq) (task1, tasks)
  print $ seq (a + sum bs) "done 2"

Define time-consuming tasks as follows:

task1 = 8^8^8 :: Integer
task2 = 8^8^8 :: Integer
tasks = [10^10..10^10+10000] :: [Integer]

Compile the code with the threaded and rtsopts flags enabled, as follows:

$ ghc -O2 --make Main.hs -threaded -rtsopts

Run it by specifying the number of cores as follows:

$ ./Main +RTS -N2