diff --git a/hawk/bin/main.c b/hawk/bin/main.c
index 018d8fb7..e09ffdee 100644
--- a/hawk/bin/main.c
+++ b/hawk/bin/main.c
@@ -356,7 +356,7 @@ static hawk_htb_walk_t print_awk_value (hawk_htb_t* map, hawk_htb_pair_t* pair,
 	return HAWK_HTB_WALK_FORWARD;
 }
 
-static int add_gvs_to_awk (hawk_t* awk, arg_t* arg)
+static int add_gvs_to_awk (hawk_t* hawk, arg_t* arg)
 {
 	if (arg->gvm.size > 0)
 	{
@@ -364,7 +364,8 @@ static int add_gvs_to_awk (hawk_t* awk, arg_t* arg)
 
 		for (i = 0; i < arg->gvm.size; i++)
 		{
-			arg->gvm.ptr[i].idx = hawk_addgbl(awk, arg->gvm.ptr[i].name);
+			arg->gvm.ptr[i].idx = arg->gvm.ptr[i].uc? hawk_addgblwithucstr(hawk, arg->gvm.ptr[i].name):
+			                                          hawk_addgblwithbcstr(hawk, arg->gvm.ptr[i].name);
 		}
 	}
 
@@ -398,7 +399,7 @@ static int apply_fs_and_gvs_to_rtx (hawk_rtx_t* rtx, arg_t* arg)
 		for (i = 0; i < arg->gvm.size; i++)
 		{
 			hawk_val_t* v;
-	
+
 			v = (arg->gvm.ptr[i].uc)? hawk_rtx_makenstrvalwithuchars(rtx, arg->gvm.ptr[i].value.ptr, arg->gvm.ptr[i].value.len):
 			                          hawk_rtx_makenstrvalwithbchars(rtx, arg->gvm.ptr[i].value.ptr, arg->gvm.ptr[i].value.len);
 			if (!v) return -1;
@@ -1012,20 +1013,6 @@ static void print_hawk_rtx_error (hawk_rtx_t* rtx)
 	);
 }
 
-hawk_htb_walk_t add_global (hawk_htb_t* map, hawk_htb_pair_t* pair, void* arg)
-{
-	hawk_t* awk = (hawk_t*)arg;
-	struct gv_t* gvmv = (struct gv_t*)HAWK_HTB_VPTR(pair);
-
-	/* the key was inserted to the table with a null at the end
-	 * and the key length was even incremetned for that.
-	 * so i can pass the pointer without other adjustments. */
-	gvmv->idx = hawk_addgbl(awk, HAWK_HTB_KPTR(pair));
-	if (gvmv->idx <= -1) return HAWK_HTB_WALK_STOP;
-	return HAWK_HTB_WALK_FORWARD;
-}
-
-
 #if 0
 static void* xma_alloc (hawk_mmgr_t* mmgr, hawk_oow_t size)
 {
diff --git a/hawk/lib/hawk.h b/hawk/lib/hawk.h
index f516d7f2..bfe64c5c 100644
--- a/hawk/lib/hawk.h
+++ b/hawk/lib/hawk.h
@@ -1737,13 +1737,13 @@ HAWK_EXPORT int hawk_findgblwithucstr (
 );
 
 #if defined(HAWK_OOCH_IS_BCH)
-#	define hawk_addgbl hawk_addgblwithbcstr
-#	define hawk_delgbl hawk_delgblwithbcstr
-#	define hawk_findgbl hawk_findgblwithbcstr
+#	define hawk_addgblwithoocstr hawk_addgblwithbcstr
+#	define hawk_delgblwithoocstr hawk_delgblwithbcstr
+#	define hawk_findgblwithoocstr hawk_findgblwithbcstr
 #else
-#	define hawk_addgbl hawk_addgblwithucstr
-#	define hawk_delgbl hawk_delgblwithucstr
-#	define hawk_findgbl hawk_findgblwithucstr
+#	define hawk_addgblwithoocstr hawk_addgblwithucstr
+#	define hawk_delgblwithoocstr hawk_delgblwithucstr
+#	define hawk_findgblwithoocstr hawk_findgblwithucstr
 #endif
 
 /**
diff --git a/hawk/lib/parse.c b/hawk/lib/parse.c
index 7f5c92bc..b9b3282b 100644
--- a/hawk/lib/parse.c
+++ b/hawk/lib/parse.c
@@ -4174,8 +4174,8 @@ static hawk_nde_t* parse_concat (hawk_t* awk, const hawk_loc_t* xloc)
 	hawk_nde_t* right = HAWK_NULL;
 	hawk_loc_t rloc;
 
-	left = parse_additive (awk, xloc);
-	if (left == HAWK_NULL) goto oops;
+	left = parse_additive(awk, xloc);
+	if (HAWK_UNLIKELY(!left)) goto oops;
 
 	do
 	{
@@ -4187,10 +4187,17 @@ static hawk_nde_t* parse_concat (hawk_t* awk, const hawk_loc_t* xloc)
 		}
 		else if (awk->opt.trait & HAWK_BLANKCONCAT)
 		{
+			/* 
+			 * [NOTE]
+			 * TOK_TILDE has been commented out in the if condition below because
+			 * BINOP_MA has lower precedence than concatenation and it is not certain
+			 * the tilde is an unary bitwise negation operator at this phase.
+			 * You may use (~10) rather than ~10 after concatenation to avoid confusion.
+			 */
 			if (MATCH(awk,TOK_LPAREN) || MATCH(awk,TOK_DOLLAR) ||
 			   /* unary operators */
 			   MATCH(awk,TOK_PLUS) || MATCH(awk,TOK_MINUS) ||
-			   MATCH(awk,TOK_LNOT) ||/* MATCH(awk,TOK_TILDE) ||*/
+			   MATCH(awk,TOK_LNOT) ||/* MATCH(awk,TOK_TILDE) ||*/ 
 			   /* increment operators */
 			   MATCH(awk,TOK_PLUSPLUS) || MATCH(awk,TOK_MINUSMINUS) ||
 			   ((awk->opt.trait & HAWK_TOLERANT) && 
@@ -4205,11 +4212,11 @@ static hawk_nde_t* parse_concat (hawk_t* awk, const hawk_loc_t* xloc)
 		else break;
 
 		rloc = awk->tok.loc;
-		right = parse_additive (awk, &rloc);
-		if (right == HAWK_NULL) goto oops;
+		right = parse_additive(awk, &rloc);
+		if (HAWK_UNLIKELY(!right)) goto oops;
 
-		tmp = new_exp_bin_node (awk, xloc, HAWK_BINOP_CONCAT, left, right);
-		if (tmp == HAWK_NULL) goto oops;
+		tmp = new_exp_bin_node(awk, xloc, HAWK_BINOP_CONCAT, left, right);
+		if (HAWK_UNLIKELY(!tmp)) goto oops;
 		left = tmp; right = HAWK_NULL;
 	}
 	while (1);
@@ -4262,8 +4269,8 @@ static hawk_nde_t* parse_unary (hawk_t* awk, const hawk_loc_t* xloc)
 	         (MATCH(awk,TOK_LNOT))?  HAWK_UNROP_LNOT:
 	         (MATCH(awk,TOK_TILDE))? HAWK_UNROP_BNOT: -1;
 
-	/*if (opcode <= -1) return parse_increment (awk);*/
-	if (opcode <= -1) return parse_exponent (awk, xloc);
+	/*if (opcode <= -1) return parse_increment(awk);*/
+	if (opcode <= -1) return parse_exponent(awk, xloc);
 
 	if (awk->opt.depth.s.expr_parse > 0 &&
 	    awk->parse.depth.expr >= awk->opt.depth.s.expr_parse)
diff --git a/hawk/lib/std.c b/hawk/lib/std.c
index c4342ba7..464b7ab2 100644
--- a/hawk/lib/std.c
+++ b/hawk/lib/std.c
@@ -3081,13 +3081,11 @@ static int add_globals (hawk_t* awk)
 {
 	xtn_t* xtn = GET_XTN(awk);
 
-	xtn->gbl_argc = hawk_addgbl(awk, HAWK_T("ARGC"));
-	xtn->gbl_argv = hawk_addgbl(awk, HAWK_T("ARGV"));
-	xtn->gbl_environ = hawk_addgbl(awk, HAWK_T("ENVIRON"));
+	xtn->gbl_argc = hawk_addgblwithoocstr(awk, HAWK_T("ARGC"));
+	xtn->gbl_argv = hawk_addgblwithoocstr(awk, HAWK_T("ARGV"));
+	xtn->gbl_environ = hawk_addgblwithoocstr(awk, HAWK_T("ENVIRON"));
 
-	return (xtn->gbl_argc <= -1 || 
-	        xtn->gbl_argv <= -1 ||
-	        xtn->gbl_environ <= -1)? -1: 0;
+	return (HAWK_UNLIKELY(xtn->gbl_argc <= -1 || xtn->gbl_argv <= -1 || xtn->gbl_environ <= -1))? -1: 0;
 }
 
 struct fnctab_t