diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,22 @@
+Copyright (c) 2016, Nikita Volkov
+
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
diff --git a/Setup.hs b/Setup.hs
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--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/interspersed.cabal b/interspersed.cabal
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--- /dev/null
+++ b/interspersed.cabal
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+name:
+  interspersed
+version:
+  0.1.0.1
+synopsis:
+  An abstraction over interspersing monadic actions
+description:
+category:
+  Control
+homepage:
+  https://github.com/nikita-volkov/interspersed 
+bug-reports:
+  https://github.com/nikita-volkov/interspersed/issues 
+author:
+  Nikita Volkov <nikita.y.volkov@mail.ru>
+maintainer:
+  Nikita Volkov <nikita.y.volkov@mail.ru>
+copyright:
+  (c) 2016, Nikita Volkov
+license:
+  MIT
+license-file:
+  LICENSE
+build-type:
+  Simple
+cabal-version:
+  >=1.10
+
+
+source-repository head
+  type:
+    git
+  location:
+    git://github.com/nikita-volkov/interspersed.git
+
+
+library
+  hs-source-dirs:
+    library
+  default-extensions:
+    Arrows, BangPatterns, ConstraintKinds, DataKinds, DefaultSignatures, DeriveDataTypeable, DeriveFoldable, DeriveFunctor, DeriveGeneric, DeriveTraversable, EmptyDataDecls, FlexibleContexts, FlexibleInstances, FunctionalDependencies, GADTs, GeneralizedNewtypeDeriving, LambdaCase, LiberalTypeSynonyms, MagicHash, MultiParamTypeClasses, MultiWayIf, NoImplicitPrelude, NoMonomorphismRestriction, OverloadedStrings, PatternGuards, ParallelListComp, QuasiQuotes, RankNTypes, RecordWildCards, ScopedTypeVariables, StandaloneDeriving, TemplateHaskell, TupleSections, TypeFamilies, TypeOperators, UnboxedTuples
+  default-language:
+    Haskell2010
+  other-modules:
+    Interspersed.Prelude
+  exposed-modules:
+    Interspersed
+  build-depends:
+    -- 
+    transformers >= 0.4 && < 0.6,
+    base-prelude < 2
diff --git a/library/Interspersed.hs b/library/Interspersed.hs
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--- /dev/null
+++ b/library/Interspersed.hs
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+module Interspersed
+(
+  Interspersed,
+  runInterspersed,
+  interspersed,
+)
+where
+
+import Interspersed.Prelude
+
+
+-- |
+-- An abstraction over interspersing monadic actions.
+newtype Interspersed m a =
+  Interspersed (ReaderT (m ()) (StateT Bool m) a)
+  deriving (Functor, Applicative, Alternative, Monad, MonadPlus)
+
+instance MonadTrans Interspersed where
+  {-# INLINE lift #-}
+  lift =
+    interspersed
+
+{-# INLINE runInterspersed #-}
+runInterspersed :: Monad m => Interspersed m a -> m () -> m a
+runInterspersed (Interspersed impl) sep =
+  {-# SCC "runInterspersed" #-} 
+  flip evalStateT True $
+  flip runReaderT sep $
+  impl
+
+-- |
+-- Lifts a monadic action. Same as 'lift'.
+{-# INLINABLE interspersed #-}
+interspersed :: Applicative m => m a -> Interspersed m a
+interspersed fx =
+  {-# SCC "interspersed" #-} 
+  Interspersed $
+  ReaderT $
+  \sep ->
+    StateT $
+    \first ->
+      fmap (\a -> (a, False)) $
+      unless first sep *> fx
diff --git a/library/Interspersed/Prelude.hs b/library/Interspersed/Prelude.hs
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--- /dev/null
+++ b/library/Interspersed/Prelude.hs
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+module Interspersed.Prelude
+( 
+  module Exports,
+  modifyM,
+  skipSepBy,
+  skipSepBy1,
+)
+where
+
+
+-- base-prelude
+-------------------------
+import BasePrelude as Exports hiding (Alt, scanl)
+
+-- transformers
+-------------------------
+import Control.Monad.IO.Class as Exports
+import Control.Monad.Trans.Class as Exports
+import Control.Monad.Trans.Except as Exports hiding (liftCallCC, liftCatch, liftListen, liftPass)
+import Control.Monad.Trans.Reader as Exports hiding (liftCallCC, liftCatch, liftListen, liftPass)
+import Control.Monad.Trans.State.Strict as Exports hiding (liftCallCC, liftCatch, liftListen, liftPass)
+import Control.Monad.Trans.Writer.Strict as Exports
+import Control.Monad.Trans.Maybe as Exports hiding (liftCallCC, liftCatch, liftListen, liftPass)
+
+-- Utils
+-------------------------
+
+{-# INLINE modifyM #-}
+modifyM :: Monad m => (a -> m a) -> StateT a m ()
+modifyM f =
+  StateT (fmap (\s -> ((), s)) . f)
+
+{-# INLINE skipSepBy #-}
+skipSepBy :: Alternative m => m () -> m () -> m ()
+skipSepBy one sep =
+  skipSepBy1 one sep <|> pure ()
+
+{-# INLINABLE skipSepBy1 #-}
+skipSepBy1 :: Alternative m => m () -> m () -> m ()
+skipSepBy1 one sep =
+  one *> remainders
+  where
+    remainders =
+      (sep *> one *> remainders) <|> pure ()