doCommand Edit = do
  l <- getCurLine
  io $ putStr $ "Replace line " ++ show l ++ ": "
  new <- io getLine
  modBuffer $ replaceLine l new
doCommand Edit = do
  l <- getCurLine
  io $ putStr $ "Replace line " ++ show l ++ ": "
  new <- io getLine
  modBuffer $ replaceLine l new
doCommand Edit = do
  l <- getCurLine
  io $ putStr $ "Replace line " ++ show l ++ ": "
  new <- io getLine
  modBuffer $ replaceLine l new