diff --git a/HISTORY b/HISTORY
index 0681834..d355df2 100755
--- a/HISTORY
+++ b/HISTORY
@@ -1,3 +1,8 @@
+Mar. 25 2015
+Changed _strupr macro to mb_strupr function
+Added an mb_strdup function
+Fixed an intermediate value disposing more than once bug
+
 Dec. 17 2014
 Fixed a calculation crash bug
 Fixed a memory leak with intermediate value
@@ -9,8 +14,8 @@ Dec. 9 2014
 Improved compatibility with BCB
 
 May. 25 2014
-Added a mb_set_inputer function which allows the user to specify an INPUT reader, thanks to Michael P. Welch for suggestion
-Added a mb_remove_reserved_func function which allows the user to disable/remove a reserved statement
+Added an mb_set_inputer function which allows the user to specify an INPUT reader, thanks to Michael P. Welch for suggestion
+Added an mb_remove_reserved_func function which allows the user to disable/remove a reserved statement
 
 May. 22 2014
 Fixed a crash bug when missing colon in a combined line, thanks to Michael P. Welch for pointing it out
diff --git a/LICENSE b/LICENSE
old mode 100644
new mode 100755
index 14006e8..73ceea8
--- a/LICENSE
+++ b/LICENSE
@@ -1,6 +1,6 @@
 The MIT License
 
-Copyright (c) 2011 - 2014 W. Renxin
+Copyright (c) 2011 - 2015 W. Renxin
 
 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
diff --git a/README.md b/README.md
old mode 100644
new mode 100755
index bdec206..ffdb731
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 ![](resource/icon.ico)
 
-Copyright (C) 2011 - 2014 W. Renxin
+Copyright (C) 2011 - 2015 W. Renxin
 
 ## Introduction
 MY-BASIC is a tiny cross-platform easy extendable BASIC interpreter written in pure C with about 6000 lines of source code. Its grammar is similar to structured BASIC in early era, but without line number. It is aimed to be either an embeddable scripting language or a standalone interpreter. The core is pretty light; all in a C source file and an associated header file. You can combine MY-BASIC with an existing C/C++/Objective-C project easily, scripting driven can make your projects more powerful, elegant and neat.
diff --git a/core/my_basic.c b/core/my_basic.c
index 07bb8ee..cb329c1 100755
--- a/core/my_basic.c
+++ b/core/my_basic.c
@@ -3,7 +3,7 @@
 **
 ** For the latest info, see https://github.com/paladin-t/my_basic/
 **
-** Copyright (C) 2011 - 2014 W. Renxin
+** Copyright (C) 2011 - 2015 W. Renxin
 **
 ** 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
@@ -78,7 +78,7 @@ extern "C" {
 /** Macros */
 #define _VER_MAJOR 1
 #define _VER_MINOR 0
-#define _VER_REVISION 45
+#define _VER_REVISION 46
 #define _MB_VERSION ((_VER_MAJOR * 0x01000000) + (_VER_MINOR * 0x00010000) + (_VER_REVISION))
 
 /* Uncomment this line to treat warnings as error */
@@ -110,21 +110,6 @@ extern "C" {
 #	define toupper(__c) ((islower(__c)) ? ((__c) - 'a' + 'A') : (__c))
 #endif /* toupper */
 
-#ifndef _MSC_VER
-#	ifndef _strupr
-		static char* _strupr(char* __s) {
-			char* t = __s;
-
-			while(*__s) {
-				*__s = toupper(*__s);
-				++__s;
-			}
-
-			return t;
-		}
-#	endif /* _strupr */
-#endif /* _MSC_VER */
-
 #define DON(__o) ((__o) ? ((_object_t*)((__o)->data)) : 0)
 
 /* Hash table size */
@@ -545,6 +530,32 @@ static void _ls_clear(_ls_node_t* list);
 static void _ls_destroy(_ls_node_t* list);
 static int _ls_free_extra(void* data, void* extra);
 
+#define _LS_FOREACH(L, O, P, E) \
+	do { \
+		_ls_node_t* __lst = L; \
+		int __opresult = _OP_RESULT_NORMAL; \
+		_ls_node_t* __tmp = 0; \
+		mb_assert(L && O); \
+		__lst = __lst->next; \
+		while(__lst) { \
+			if(P != 0) { \
+				P(__lst->data, __lst->extra, E); \
+			} \
+			__opresult = O(__lst->data, __lst->extra); \
+			__tmp = __lst; \
+			__lst = __lst->next; \
+			if(_OP_RESULT_NORMAL == __opresult) { \
+			} else if(_OP_RESULT_DEL_NODE == __opresult) { \
+				__tmp->prev->next = __lst; \
+				if(__lst) { \
+					__lst->prev = __tmp->prev; \
+				} \
+				safe_free(__tmp); \
+			} else { \
+			} \
+		} \
+	} while(0)
+
 /** Dictionary */
 static unsigned int _ht_hash_string(void* ht, void* d);
 static unsigned int _ht_hash_int(void* ht, void* d);
@@ -583,6 +594,8 @@ static void* mb_malloc(size_t s);
 static void* mb_realloc(void** p, size_t s);
 static void mb_free(void* p);
 
+static char* mb_strupr(char* s);
+
 #define safe_free(__p) do { if(__p) { mb_free(__p); __p = 0; } else { mb_assert(0 && "Memory already released"); } } while(0)
 
 /** Expression processing */
@@ -668,6 +681,7 @@ static int _remove_source_object(void* data, void* extra);
 static int _compare_numbers(const _object_t* first, const _object_t* second);
 static int _public_value_to_internal_object(mb_value_t* pbl, _object_t* itn);
 static int _internal_object_to_public_value(_object_t* itn, mb_value_t* pbl);
+static void _try_clear_intermediate_value(void* data, void* extra, mb_interpreter_t* s);
 
 static int _execute_statement(mb_interpreter_t* s, _ls_node_t** l);
 static int _skip_to(mb_interpreter_t* s, _ls_node_t** l, mb_func_t f, _data_e t);
@@ -1531,6 +1545,17 @@ void mb_free(void* p) {
 	free(p);
 }
 
+char* mb_strupr(char* s) {
+	char* t = s;
+
+	while(*s) {
+		*s = toupper(*s);
+		++s;
+	}
+
+	return t;
+}
+
 /** Expression processing */
 bool_t _is_operator(mb_func_t op) {
 	/* Determine whether a function is an operator */
@@ -1939,11 +1964,13 @@ int _calc_expression(mb_interpreter_t* s, _ls_node_t** l, _object_t** val) {
 		}
 	}
 	if(guard_val != c && _ls_try_remove(garbage, c, _ls_cmp_data, NULL)) {
+		_try_clear_intermediate_value(c, 0, s);
+
 		_destroy_object(c, 0);
 	}
 
 _exit:
-	_ls_foreach(garbage, _destroy_object);
+	_LS_FOREACH(garbage, _destroy_object, _try_clear_intermediate_value, s);
 	_ls_destroy(garbage);
 	_ls_foreach(optr, _destroy_object_non_syntax);
 	_ls_foreach(opnd, _destroy_object_non_syntax);
@@ -2983,6 +3010,24 @@ int _internal_object_to_public_value(_object_t* itn, mb_value_t* pbl) {
 	return result;
 }
 
+void _try_clear_intermediate_value(void* data, void* extra, mb_interpreter_t* s) {
+	/* Try clear the intermediate value when destroying an object */
+	_object_t* obj = 0;
+	_running_context_t* running = 0;
+
+	mb_assert(s);
+
+	if(data == 0)
+		return;
+
+	obj = (_object_t*)data;
+	running = (_running_context_t*)(s->running_context);
+
+	if(obj->type == _DT_STRING && running->intermediate_value.type == MB_DT_STRING && obj->data.string == running->intermediate_value.value.string) {
+		running->intermediate_value.type = MB_DT_NIL;
+	}
+}
+
 int _execute_statement(mb_interpreter_t* s, _ls_node_t** l) {
 	/* Execute the ast, core execution function */
 	int result = MB_FUNC_OK;
@@ -3130,7 +3175,7 @@ int _register_func(mb_interpreter_t* s, const char* n, mb_func_t f, bool_t local
 		size_t _sl = strlen(n);
 		name = (char*)mb_malloc(_sl + 1);
 		memcpy(name, n, _sl + 1);
-		_strupr(name);
+		mb_strupr(name);
 		result += _ht_set_or_insert(scope, (void*)name, (void*)(intptr_t)f);
 	} else {
 		_set_current_error(s, SE_CM_FUNC_EXISTS);
@@ -3158,7 +3203,7 @@ int _remove_func(mb_interpreter_t* s, const char* n, bool_t local) {
 		size_t _sl = strlen(n);
 		name = (char*)mb_malloc(_sl + 1);
 		memcpy(name, n, _sl + 1);
-		_strupr(name);
+		mb_strupr(name);
 		result += _ht_remove(scope, (void*)name, _ls_cmp_extra_string);
 		safe_free(name);
 	} else {
@@ -4025,6 +4070,18 @@ int mb_gets(char* buf, int s) {
 	return result;
 }
 
+char* mb_strdup(char* val, unsigned size) {
+	/* Duplicate a string for internal use */
+	char* result = 0;
+
+	if(val != 0) {
+		result = (char*)mb_malloc(size);
+		memcpy(result, val, size);
+	}
+
+	return result;
+}
+
 /* ========================================================} */
 
 /*
diff --git a/core/my_basic.h b/core/my_basic.h
index 65aa68d..a0174c5 100755
--- a/core/my_basic.h
+++ b/core/my_basic.h
@@ -3,7 +3,7 @@
 **
 ** For the latest info, see https://github.com/paladin-t/my_basic/
 **
-** Copyright (C) 2011 - 2014 W. Renxin
+** Copyright (C) 2011 - 2015 W. Renxin
 **
 ** 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
@@ -252,6 +252,8 @@ MBAPI int mb_set_inputer(mb_interpreter_t* s, mb_input_func_t p);
 
 MBAPI int mb_gets(char* buf, int s);
 
+MBAPI char* mb_strdup(char* val, unsigned size);
+
 #ifdef MB_COMPACT_MODE
 #	pragma pack()
 #endif /* MB_COMPACT_MODE */
diff --git a/output/my_basic.exe b/output/my_basic.exe
index ec874b1..740a3fc 100755
Binary files a/output/my_basic.exe and b/output/my_basic.exe differ
diff --git a/output/my_basic_mac b/output/my_basic_mac
old mode 100644
new mode 100755
index 3fd4de8..c09e1ff
Binary files a/output/my_basic_mac and b/output/my_basic_mac differ
diff --git a/resource/icon.ico b/resource/icon.ico
old mode 100644
new mode 100755
diff --git a/resource/my_basic.aps b/resource/my_basic.aps
old mode 100644
new mode 100755
diff --git a/resource/my_basic.rc b/resource/my_basic.rc
index 8abc5cd..1de3c05 100755
--- a/resource/my_basic.rc
+++ b/resource/my_basic.rc
@@ -81,13 +81,13 @@ BEGIN
             VALUE "Comments", "MY-BASIC"
             VALUE "CompanyName", "W. Renxin"
             VALUE "FileDescription", "MY-BASIC interpreter"
-            VALUE "FileVersion", "1, 0, 0, 45"
+            VALUE "FileVersion", "1, 0, 0, 46"
             VALUE "InternalName", "my_basic"
-            VALUE "LegalCopyright", "Copyright (C) 2011 - 2014 W. Renxin"
+            VALUE "LegalCopyright", "Copyright (C) 2011 - 2015 W. Renxin"
             VALUE "LegalTrademarks", "MY-BASIC"
             VALUE "OriginalFilename", "my_basic.exe"
             VALUE "ProductName", "MY-BASIC"
-            VALUE "ProductVersion", "1, 0, 0, 45"
+            VALUE "ProductVersion", "1, 0, 0, 46"
         END
     END
     BLOCK "VarFileInfo"
diff --git a/resource/resource.h b/resource/resource.h
old mode 100644
new mode 100755
diff --git a/sample/sample01.bas b/sample/sample01.bas
old mode 100644
new mode 100755
index 6c8d63b..73a14c9
--- a/sample/sample01.bas
+++ b/sample/sample01.bas
@@ -1,5 +1,5 @@
 ' This script is an example of MY-BASIC
-' Copyright (c) 2011 - 2014 W. Renxin. All rights reserved.
+' Copyright (c) 2011 - 2015 W. Renxin. All rights reserved.
 ' For more information, see https://github.com/paladin-t/my_basic/
 
 s$ = "hello "
diff --git a/sample/sample02.bas b/sample/sample02.bas
old mode 100644
new mode 100755
index a4a303a..2f6fa0b
--- a/sample/sample02.bas
+++ b/sample/sample02.bas
@@ -1,5 +1,5 @@
 ' This script is an example of MY-BASIC
-' Copyright (c) 2011 - 2014 W. Renxin. All rights reserved.
+' Copyright (c) 2011 - 2015 W. Renxin. All rights reserved.
 ' For more information, see https://github.com/paladin-t/my_basic/
 
 e = 50
diff --git a/sample/sample03.bas b/sample/sample03.bas
old mode 100644
new mode 100755
index 6019567..57847a9
--- a/sample/sample03.bas
+++ b/sample/sample03.bas
@@ -1,5 +1,5 @@
 ' This script is an example of MY-BASIC
-' Copyright (c) 2011 - 2014 W. Renxin. All rights reserved.
+' Copyright (c) 2011 - 2015 W. Renxin. All rights reserved.
 ' For more information, see https://github.com/paladin-t/my_basic/
 
 PRINT "Input: "
diff --git a/sample/sample04.bas b/sample/sample04.bas
old mode 100644
new mode 100755
index a2d4a16..0bc2466
--- a/sample/sample04.bas
+++ b/sample/sample04.bas
@@ -1,5 +1,5 @@
 ' This script is an example of MY-BASIC
-' Copyright (c) 2011 - 2014 W. Renxin. All rights reserved.
+' Copyright (c) 2011 - 2015 W. Renxin. All rights reserved.
 ' For more information, see https://github.com/paladin-t/my_basic/
 
 BEGIN:
diff --git a/shell/main.c b/shell/main.c
index 98cfa0a..15fdc5f 100755
--- a/shell/main.c
+++ b/shell/main.c
@@ -3,7 +3,7 @@
 **
 ** For the latest info, see https://github.com/paladin-t/my_basic/
 **
-** Copyright (C) 2011 - 2014 W. Renxin
+** Copyright (C) 2011 - 2015 W. Renxin
 **
 ** 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
@@ -331,7 +331,7 @@ static void _kill_program(const char* path) {
 
 static void _show_tip(void) {
 	printf("MY-BASIC Interpreter Shell - %s.\n", mb_ver_string());
-	printf("Copyright (C) 2011 - 2014 W. Renxin. All Rights Reserved.\n");
+	printf("Copyright (C) 2011 - 2015 W. Renxin. All Rights Reserved.\n");
 	printf("For more information, see https://github.com/paladin-t/my_basic/.\n");
 	printf("Input HELP and hint enter to view help information.\n");
 }