Dear reader, I wonder whether there is a 'general' working solution to include files within a parsec parser. Without the need of unsafePerformIO. Appending an example program, using unsafePerformIO. Thanx for reading. Greetings, Leonard Siebeneicher --- Begin: experiment.hs --- import Text.ParserCombinators.Parsec import System.IO.Unsafe my_str :: Parser String my_str = many1 anyToken wrap_input :: Parser String -> Parser String wrap_input p = do i <- getInput setInput readI a <- my_str setInput i b <- my_str return $ a ++ " //\n\n " ++ b where {- Aaaah ... any solution without unsafePerformIO? -} readI = unsafePerformIO (readFile "experiment.hs") main = case parse (wrap_input my_str) "" "eintest" of Left err -> putStrLn "Error raised" Right ostr -> putStrLn ostr --- End: experiment.hs --- ___ Thinking about a special type like data MyInclude = PlainText String | IncludeFile String the parser could generate [MyInclude] data, but it does not work generally.