Parsecでアノテーション風にテキストの一部をファイルで置換する ref: http://qiita.com/ykst/items/77aa62ba539eb23bb1d6

file2.txt

ghc --make gen.hs
./gen sample.js

gen.hs

module Main where
import System.Environment (getArgs)
import Text.Parsec
import Text.Parsec.String
import Control.Monad.Trans (liftIO)
import Control.Applicative hiding ((<|>), many, optional)

annotateP :: ParsecT String () IO String
annotateP = (try (wrapP includeP)) <|> (many anyChar)
    where 
    wrapP innerP = 
        (++) <$> many (satisfy ('@' /=)) <*> ((++) <$> innerP <*> many anyChar)
    includeP = 
        (string "@include" <* spaces) >> 
        (between (char '(' <* spaces) (char ')') (many (noneOf ") \t") <* spaces)) >>= 
        (liftIO . readFile)

main = getArgs >>= \args -> case args of
    [f] -> readFile f >>= convert . lines 
    _ -> putStrLn "specify one file"
    where
    convert [] = pure ()
    convert (l:ls) = 
        runParserT annotateP () "" l >>= either (error . show) putStrLn >> convert ls

sample.js

(function(global) {
    (function() {
        @include(a.js)
        @include(b.js)
        @include(c.js)
    }).apply(global);

    // do something
}({}));