diff --git a/prototype.cabal b/prototype.cabal
--- a/prototype.cabal
+++ b/prototype.cabal
@@ -2,7 +2,7 @@
 cabal-version:	>= 1.2
 
 name:		prototype
-version:	0.3
+version:	0.4.1
 stability:	experimental
 author:		Yoshikuni Jujo <PAF01143@nifty.ne.jp>
 maintainer:	Yoshikuni Jujo <PAF01143@nifty.ne.jp>
@@ -26,17 +26,19 @@
 		>
 		> main :: IO ()
 		> main = fmap fst $ flip runPT initPTEnv $ do
-		>	dog <- clone object
-		>	name	<- makeMember "name"
-		>	setName	<- makeMember "setName"
-		>	sit	<- makeMember "sit"
-		>	setMethod dog setName $ \this [ n ] -> do
-		>		setMember this name n
-		>		return [ ]
-		>	setMethod dog sit $ \this _ -> do
-		>		n <- member this name
-		>		liftPT $ putStrLn $ fromPrimStr n ++ " sitting."
-		>		return [ ]
+		>	( dog, setName, sit ) <- package "dog" $ do
+		>		dog <- clone object
+		>		name	<- makeMember "name"
+		>		setName	<- makeMember "setName"
+		>		sit	<- makeMember "sit"
+		>		setMethod dog setName $ \this [ n ] -> do
+		>			setMember this name n
+		>			return [ ]
+		>		setMethod dog sit $ \this _ -> do
+		>			n <- member this name
+		>			liftPT $ putStrLn $ fromPrimStr n ++ " sitting."
+		>			return [ ]
+		>		return ( dog, setName, sit )
 		>	myDog <- clone dog
 		>	method myDog setName [ primStr "John" ]
 		>	method myDog sit [ ]
diff --git a/src/Control/Prototype.hs b/src/Control/Prototype.hs
--- a/src/Control/Prototype.hs
+++ b/src/Control/Prototype.hs
@@ -16,6 +16,8 @@
 	setMember,
 	setMethod,
 
+	package,
+
 	liftPT,
 	primInt,
 	primStr,
@@ -27,7 +29,7 @@
 
 import Prelude hiding ( head )
 import "monads-tf" Control.Monad.State (
-	StateT, runStateT, lift, MonadIO, liftIO, modify, gets )
+	StateT, runStateT, lift, MonadIO, liftIO, put, get, gets )
 import Data.List ( (\\) )
 import Data.Maybe ( fromMaybe, listToMaybe )
 
@@ -47,10 +49,16 @@
 liftPT :: Monad m => m a -> PTMonad m a
 liftPT = lift
 
-type PTEnv m = [ ObjectBody m ]
+data PTEnv m = PTEnv {
+	packageName	:: String,
+	objectBodys	:: [ ObjectBody m ]
+ } deriving Show
 
 initPTEnv :: PTEnv m
-initPTEnv = [ ObjectBody object [ ] ]
+initPTEnv = PTEnv {
+	packageName	= "main",
+	objectBodys	= [ ObjectBody object [ ] ]
+ }
 
 data Object =
 	ObjectId { fromObjId :: Int } |
@@ -85,18 +93,20 @@
 --------------------------------------------------------------------------------
 
 getNewId :: Monad m => PTMonad m Object
-getNewId = gets $
-	ObjectId . head err . ( [ 1 .. ] \\ ) .	map ( fromObjId . objectId )
+getNewId = gets $ ObjectId . head err . ( [ 1 .. ] \\ ) .
+	map ( fromObjId . objectId ) . objectBodys
 	where
 	err = error "too many objects"
 
 getObject :: Monad m => Object -> PTMonad m ( ObjectBody m )
-getObject obj =	gets $ head err . filter ( ( == obj ) . objectId )
+getObject obj =	gets $ head err . filter ( ( == obj ) . objectId ) . objectBodys
 	where
 	err = error $ "no such object: " ++ show obj
 
 putObject :: Monad m => ObjectBody m -> PTMonad m ()
-putObject = modify . ( : )
+putObject objBody = do
+	env@PTEnv { objectBodys = obs } <- get
+	put env { objectBodys = objBody : obs }
 
 clone :: Monad m => Object -> PTMonad m Object
 clone obj = do
@@ -106,7 +116,8 @@
 	return newId
 
 makeMember :: Monad m => String -> PTMonad m Member
-makeMember = return . Member
+makeMember name =
+	mmap ( Member . ( ++ name ) . ( ++ "::" ) ) $ gets packageName
 
 member :: Monad m => Object -> Member -> PTMonad m Object
 member obj mem =
@@ -128,6 +139,15 @@
 	newId <- getNewId
 	putObject $ Method newId met
 	setMember obj mem newId
+
+package :: Monad m => String -> PTMonad m a -> PTMonad m a
+package pkg act = do
+	env0@PTEnv { packageName = oldPkg } <- get
+	put env0 { packageName = pkg }
+	ret <- act
+	env1 <- get
+	put env1 { packageName = oldPkg }
+	return ret
 
 printMemberName :: MonadIO m => Member -> m ()
 printMemberName ( Member name ) = liftIO $ putStrLn name