This is a simple example of using Shake (version 0.10.2). It demonstrates how to copy an input file to an output file with a file that is an additional dependency for a target even though it is not used in the rule itself.

copyWithDependency.hs

{-# OPTIONS_GHC -Wall #-}
module Main where
import Development.Shake

main :: IO ()
main = shakeArgs shakeOptions $ do
  want ["output-file"]
  "output-file" *> \dst -> do
    need ["dependency-file"]
    copyFile' "input-file" dst