diff --git a/egison.cabal b/egison.cabal
--- a/egison.cabal
+++ b/egison.cabal
@@ -1,5 +1,5 @@
 Name:                egison
-Version:             2.3.3
+Version:             2.3.4
 Synopsis:            An Interpreter for the Programming Language Egison
 Description:         An interpreter for the programming language Egison.
                      A feature of Egison is the strong pattern match facility.
diff --git a/hs-src/Language/Egison/Core.hs b/hs-src/Language/Egison/Core.hs
--- a/hs-src/Language/Egison/Core.hs
+++ b/hs-src/Language/Egison/Core.hs
@@ -265,16 +265,14 @@
 cEval1 (Closure env (MatchExpr tgtExpr typExpr mcs)) = do
   tgtObjRef <- liftIO $ makeClosure env tgtExpr
   typObjRef <- liftIO $ makeClosure env typExpr
-  retRef <- mcLoop tgtObjRef typObjRef mcs
-  cRefEval1 retRef
+  mcLoop tgtObjRef typObjRef mcs
  where mcLoop _ _ [] = throwError $ Default "end of match clauses"
        mcLoop tgtObjRef typObjRef ((patExpr, body):rest) = do
          patObjRef <- liftIO $ makeClosure env patExpr
          matchs <- patternMatch MOne [(MState [] [(MAtom (PClosure [] patObjRef) tgtObjRef typObjRef)])]
          case matchs of
            [match] -> do newEnv <- liftIO $ extendEnv env match
-                         objRef <- liftIO $ newIORef (Closure newEnv body)
-                         return objRef
+                         cEval1 (Closure newEnv body)
            [] -> mcLoop tgtObjRef typObjRef rest
 cEval1 (Closure env (LoopExpr loopVar indexVar rangeExpr loopExpr tailExpr)) = do
   rangeObjRef <- liftIO $ makeClosure env rangeExpr
@@ -672,23 +670,29 @@
 primitivePatternMatchList _ _ = throwError (Default "primitivePatternMatchList : number of patterns and targets are different")
 
 
+objectRefToInnerRefs :: ObjectRef -> IOThrowsError [InnerValRef]
+objectRefToInnerRefs objRef = do
+  obj <- cRefEval1 objRef
+  case obj of
+    Intermidiate (ICollection innerRefs) -> return innerRefs
+    Value (Collection innerVals) -> do
+      objRefs <- innerValsToObjRefList innerVals
+      return $ map IElement objRefs
+
 isEmptyCollection :: ObjectRef -> IOThrowsError Bool
 isEmptyCollection objRef = do
   obj <- cRefEval1 objRef
   case obj of
-    Intermidiate (ICollection innerRefs) -> isEmptyInnerRefs innerRefs
+    Intermidiate (ICollection []) -> return True
+    Intermidiate (ICollection ((IElement _):_)) -> return False
+    Intermidiate (ICollection ((ISubCollection subObjRef):rest)) -> do
+      innerRefs <- objectRefToInnerRefs subObjRef
+      liftIO $ writeIORef objRef $ Intermidiate $ ICollection $ innerRefs ++ rest
+      isEmptyCollection objRef
+    Value (Collection []) -> return True
     Value (Collection innerVals) -> isEmptyInnerVals innerVals
     _ -> throwError $ Default $ "isEmptyCollection: not collection:" ++ show obj
 
-isEmptyInnerRefs :: [InnerValRef] -> IOThrowsError Bool
-isEmptyInnerRefs [] = return True
-isEmptyInnerRefs ((IElement _):_) = return False
-isEmptyInnerRefs ((ISubCollection objRef):rest) = do
-  b <- isEmptyCollection objRef
-  if b
-    then isEmptyInnerRefs rest
-    else return False
-
 isEmptyInnerVals :: [InnerVal] -> IOThrowsError Bool
 isEmptyInnerVals [] = return True
 isEmptyInnerVals ((Element _):_) = return False
@@ -703,21 +707,19 @@
 isEmptyCollectionForSnoc objRef = do
   obj <- cRefEval1 objRef
   case obj of
-    Intermidiate (ICollection innerRefs) -> isEmptyInnerRefsForSnoc innerRefs
+    Intermidiate (ICollection ((IElement _):_)) -> return False
+    Intermidiate (ICollection innerRefs) -> do
+      case reverse innerRefs of
+        [] -> return True
+        ((IElement _):_) -> return False
+        ((ISubCollection subObjRef):rest) -> do
+          subInnerRefs <- objectRefToInnerRefs subObjRef
+          liftIO $ writeIORef objRef $ Intermidiate $ ICollection $ reverse rest ++ reverse subInnerRefs
+          isEmptyCollectionForSnoc objRef
+    Value (Collection []) -> return True
     Value (Collection innerVals) -> isEmptyInnerValsForSnoc innerVals
     _ -> throwError $ Default $ "isEmptyCollectionForSnoc: not collection:" ++ show obj
 
-isEmptyInnerRefsForSnoc :: [InnerValRef] -> IOThrowsError Bool
-isEmptyInnerRefsForSnoc innerRefs =
-  case reverse innerRefs of
-    [] -> return True
-    ((IElement _):_) -> return False
-    ((ISubCollection objRef):rest) -> do
-      b <- isEmptyCollectionForSnoc objRef
-      if b
-        then isEmptyInnerRefsForSnoc $ reverse rest
-        else return False
-
 isEmptyInnerValsForSnoc :: [InnerVal] -> IOThrowsError Bool
 isEmptyInnerValsForSnoc innerVals =
   case reverse innerVals of
@@ -730,7 +732,6 @@
         then isEmptyInnerValsForSnoc $ reverse rest
         else return False
 
-
 consDestruct :: ObjectRef -> IOThrowsError (ObjectRef, ObjectRef)
 consDestruct objRef = do
   obj <- cRefEval1 objRef
@@ -812,7 +813,7 @@
                 rdcObj <- liftIO $ readIORef rdcObjRef
                 case rdcObj of
                   Value (Collection innerVals2) -> do
-                    rdcObjRef2 <- liftIO $ newIORef $ Value $ Collection $ (reverse rest) ++ [(SubCollection (Collection innerVals))]
+                    rdcObjRef2 <- liftIO $ newIORef $ Value $ Collection $ (reverse rest) ++ [(SubCollection (Collection innerVals2))]
                     return (racObjRef, rdcObjRef2)
                   _ -> throwError $ Default "snocDestructInnerVals: cannot reach here!"