diff --git a/csv-enumerator.cabal b/csv-enumerator.cabal
--- a/csv-enumerator.cabal
+++ b/csv-enumerator.cabal
@@ -1,5 +1,5 @@
 Name:                csv-enumerator
-Version:             0.9.0
+Version:             0.9.2
 Synopsis:            A flexible, fast, enumerator-based CSV parser library for Haskell.  
 Homepage:            http://github.com/ozataman/csv-enumerator
 License:             BSD3
@@ -60,15 +60,16 @@
   Other-modules:
       Data.CSV.Enumerator.Types
   build-depends:
-      attoparsec >= 0.8 && < 0.10
-    , attoparsec-enumerator >= 0.2.0.3
+      attoparsec >= 0.8
+    , attoparsec-enumerator >= 0.2
     , base >= 4 && < 5
     , containers >= 0.3
     , directory
     , bytestring
-    , enumerator >= 0.4.5 && < 0.5
+    , enumerator >= 0.4.5
     , transformers >= 0.2
     , safe
     , unix-compat >= 0.2.1.1
   extensions:
     ScopedTypeVariables
+  ghc-options: -funbox-strict-fields
diff --git a/src/Data/CSV/Enumerator.hs b/src/Data/CSV/Enumerator.hs
--- a/src/Data/CSV/Enumerator.hs
+++ b/src/Data/CSV/Enumerator.hs
@@ -32,6 +32,7 @@
 
   -- * Mapping Over CSV Files
   , mapCSVFile
+  , mapAccumCSVFile
   , mapIntoHandle
 
   -- * Primitive Iteratees
@@ -307,6 +308,30 @@
 
 
 ------------------------------------------------------------------------------
+-- | Map-accumulate over a CSV file. Similar to 'mapAccumL' in 'Data.List'.
+mapAccumCSVFile
+  :: (CSVeable r)
+  => FilePath
+  -> CSVSettings
+  -> (acc -> r -> (acc, [r]))
+  -> acc
+  -> FilePath
+  -> IO (Either SomeException acc)
+mapAccumCSVFile fi s f acc fo = do
+  res <- foldCSVFile fi s iter (acc, (Nothing, 0))
+  return $ fst `fmap` res
+  where
+    iter (a, outa) (ParsedRow (Just !r)) = foldM chain (a', outa) rs
+      where (a', rs) = f a r
+    iter (a, outa) x = do
+      outa' <- fileSink s fo outa x
+      return $ (a, outa')
+    chain (a, outa) !r = do
+      outa' <- fileSink s fo outa (ParsedRow (Just r))
+      return $ (a, outa')
+
+
+------------------------------------------------------------------------------
 readCSVFile :: (CSVeable r) => CSVSettings  -- ^ CSV settings
             -> FilePath   -- ^ FilePath
             -> IO (Either SomeException [r])  -- ^ Collected data
@@ -337,19 +362,19 @@
              -> [r]   -- ^ Data to be output
              -> IO Int  -- ^ Number of rows written
 appendCSVFile s fp rs = 
-  let doOutput (c,h) = when c (writeHeaders s h rs) >> outputRowsIter h
+  let doOutput (c,h) = when c (writeHeaders s h rs >> return ()) >> outputRowsIter h
       outputRowsIter h = foldM (step h) 0  . map (rowToStr s) $ rs
       step h acc x = (B.hPutStrLn h x) >> return (acc+1)
       chkOpen = do
-        writeHeaders <- do
+        wrHeader <- do
           fe <- doesFileExist fp 
           if fe
-          	then do
-          	  fs <- getFileStatus fp >>= return . fileSize
-          	  return $ if fs > 0 then False else True
+            then do
+              fs <- getFileStatus fp >>= return . fileSize
+              return $ if fs > 0 then False else True
             else return True
         h <- openFile fp AppendMode
-        return (writeHeaders, h)
+        return (wrHeader, h)
   in bracket
       (chkOpen)
       (hClose . snd)
@@ -380,10 +405,10 @@
 
 
 
-writeHeaders :: CSVeable r => CSVSettings -> Handle -> [r] -> IO ()
+writeHeaders :: CSVeable r => CSVSettings -> Handle -> [r] -> IO Bool
 writeHeaders s h rs = case fileHeaders rs of
-  Just hs -> B.hPutStrLn h . rowToStr s $ hs
-  Nothing -> return ()
+  Just hs -> (B.hPutStrLn h . rowToStr s) hs >> return True
+  Nothing -> return False
 
 
 outputRowIter :: CSVeable r => CSVSettings -> Handle -> r -> E.Iteratee B.ByteString IO ()
@@ -468,10 +493,12 @@
   where
     f' acc EOF = return acc
     f' acc (ParsedRow Nothing) = return acc
-    f' (False, _) r'@(ParsedRow (Just r)) = do
+    f' (False, i) r'@(ParsedRow (Just r)) = do
       rs <- f r
-      when outh $ writeHeaders csvs h rs
-      f' (True, 0) r'
+      headerDone <- if outh then writeHeaders csvs h rs else return True
+      if headerDone 
+      	then f' (headerDone, 0) r'  -- Headers are done, now process row
+        else return (False, i+1)    -- Problem in this row, move on to next
     f' (True, !i) (ParsedRow (Just r)) = do
       rs <- f r
       outputRows csvs h rs
@@ -487,9 +514,13 @@
                                        in a' `seq` yield a' (E.Chunks [])
 collectRows acc (ParsedRow Nothing) = yield acc (E.Chunks [])
 
--- * Parsers
 
-rowParser :: (Monad m, MonadIO m) => CSVSettings -> E.Iteratee B.ByteString m (Maybe Row)
+------------------------------------------------------------------------------
+-- Parsers
+
+rowParser 
+  :: (Monad m, MonadIO m) 
+  => CSVSettings -> E.Iteratee B.ByteString m (Maybe Row)
 rowParser csvs = E.catchError p handler 
   where 
     p = iterParser $ row csvs
@@ -497,6 +528,7 @@
       liftIO $ putStrLn ("Error in parsing: " ++ show e)
       yield Nothing (E.Chunks [])
       
+
 row :: CSVSettings -> Parser (Maybe Row)
 row csvs = csvrow csvs <|> badrow
 
@@ -506,8 +538,8 @@
 
 csvrow :: CSVSettings -> Parser (Maybe Row)
 csvrow c = 
-  let !rowbody = (quotedField' <|> (field c)) `sepBy` C8.char (csvSep c)
-      !properrow = rowbody <* (C8.endOfLine <|> P.endOfInput)
+  let rowbody = (quotedField' <|> (field c)) `sepBy` C8.char (csvSep c)
+      properrow = rowbody <* (C8.endOfLine <|> P.endOfInput)
       quotedField' = case csvQuoteChar c of
           Nothing -> mzero
           Just q' -> try (quotedField q')
@@ -516,7 +548,7 @@
     return $ Just res
 
 field :: CSVSettings -> Parser Field
-field s = P.takeWhile (isFieldChar s) <?> "Parsing a regular field"
+field s = P.takeWhile (isFieldChar s) 
 
 isFieldChar s = notInClass xs'
   where xs = csvSep s : "\n\r"
@@ -525,10 +557,13 @@
           Just x -> x : xs
 
 quotedField :: Char -> Parser Field
-quotedField c = let w = c2w c in do
-  (C8.char c) <?> "Quote start"
-  f <- many (notWord8 w <|> (string (B.pack $ [w,w]) *> return w))
-  (C8.char c) <?> "Quote end"
-  return $ B.pack f
+quotedField c = 
+  let quoted = string dbl *> return c
+      dbl = B8.pack [c,c]
+  in do
+  C8.char c 
+  f <- many (C8.notChar c <|> quoted)
+  C8.char c 
+  return $ B8.pack f
 
 
diff --git a/src/Data/CSV/Enumerator/Types.hs b/src/Data/CSV/Enumerator/Types.hs
--- a/src/Data/CSV/Enumerator/Types.hs
+++ b/src/Data/CSV/Enumerator/Types.hs
@@ -13,16 +13,16 @@
 data CSVSettings = CSVS
   { 
     -- | Separator character to be used in between fields
-    csvSep :: Char          
+    csvSep :: !Char          
 
     -- | Quote character that may sometimes be present around fields. If 'Nothing' is given, the library will never expect quotation even if it is present.
-  , csvQuoteChar :: Maybe Char
+  , csvQuoteChar :: !(Maybe Char)
   
     -- | Quote character that should be used in the output.
-  , csvOutputQuoteChar :: Maybe Char
+  , csvOutputQuoteChar :: !(Maybe Char)
   
     -- | Field separator that should be used in the output.
-  , csvOutputColSep :: Char
+  , csvOutputColSep :: !Char
   } deriving (Read, Show, Eq)
 
 -- | Default settings for a CSV file. 
diff --git a/test/csv-enumerator-test.cabal b/test/csv-enumerator-test.cabal
--- a/test/csv-enumerator-test.cabal
+++ b/test/csv-enumerator-test.cabal
@@ -9,14 +9,7 @@
 Category:            Data
 Build-type:          Simple
 Cabal-version:       >=1.2
-Description:
-  For more information and examples, check out the README at:
-  <http://github.com/ozataman/csv-enumerator>.
-  
-  The API is fairly well documented and I would encourage you to keep your
-  haddocks handy.
 
-
 extra-source-files:
   README.markdown
 
@@ -45,3 +38,32 @@
   extensions:
     ScopedTypeVariables
     OverloadedStrings
+
+
+Executable bench
+  main-is: Bench.hs
+  hs-source-dirs: ./ ../src
+  Other-modules:
+      Data.CSV.Enumerator.Types
+      Data.CSV.Enumerator
+  build-depends:
+      attoparsec >= 0.8 && < 0.10
+    , attoparsec-enumerator >= 0.2.0.3
+    , base >= 4 && < 5
+    , containers >= 0.3
+    , directory
+    , bytestring
+    , enumerator >= 0.4.5 && < 0.5
+    , transformers >= 0.2
+    , safe
+    , unix-compat >= 0.2.1.1
+    , test-framework
+    , test-framework-quickcheck2
+    , test-framework-hunit
+    , QuickCheck >= 2
+    , HUnit >= 1.2
+  extensions:
+    ScopedTypeVariables
+    OverloadedStrings
+  ghc-options: -rtsopts 
+  ghc-prof-options: -rtsopts -caf-all -auto-all