diff --git a/hawk/lib/run.c b/hawk/lib/run.c
index 8cbeafe5..469c53cc 100644
--- a/hawk/lib/run.c
+++ b/hawk/lib/run.c
@@ -5570,13 +5570,13 @@ static hawk_val_t* eval_binop_ma (hawk_rtx_t* run, hawk_nde_t* left, hawk_nde_t*
 	HAWK_ASSERT (left->next == HAWK_NULL);
 	HAWK_ASSERT (right->next == HAWK_NULL);
 
-	lv = eval_expression (run, left);
-	if (lv == HAWK_NULL) return HAWK_NULL;
+	lv = eval_expression(run, left);
+	if (HAWK_UNLIKELY(!lv)) return HAWK_NULL;
 
 	hawk_rtx_refupval (run, lv);
 
-	rv = eval_expression0 (run, right);
-	if (rv == HAWK_NULL)
+	rv = eval_expression0(run, right);
+	if (HAWK_UNLIKELY(!rv))
 	{
 		hawk_rtx_refdownval (run, lv);
 		return HAWK_NULL;
@@ -5584,7 +5584,7 @@ static hawk_val_t* eval_binop_ma (hawk_rtx_t* run, hawk_nde_t* left, hawk_nde_t*
 
 	hawk_rtx_refupval (run, rv);
 
-	res = eval_binop_match0 (run, lv, rv, &left->loc, &right->loc, 1);
+	res = eval_binop_match0(run, lv, rv, &left->loc, &right->loc, 1);
 
 	hawk_rtx_refdownval (run, rv);
 	hawk_rtx_refdownval (run, lv);
@@ -5599,13 +5599,13 @@ static hawk_val_t* eval_binop_nm (hawk_rtx_t* run, hawk_nde_t* left, hawk_nde_t*
 	HAWK_ASSERT (left->next == HAWK_NULL);
 	HAWK_ASSERT (right->next == HAWK_NULL);
 
-	lv = eval_expression (run, left);
-	if (lv == HAWK_NULL) return HAWK_NULL;
+	lv = eval_expression(run, left);
+	if (HAWK_UNLIKELY(!lv)) return HAWK_NULL;
 
 	hawk_rtx_refupval (run, lv);
 
-	rv = eval_expression0 (run, right);
-	if (rv == HAWK_NULL)
+	rv = eval_expression0(run, right);
+	if (HAWK_UNLIKELY(!rv))
 	{
 		hawk_rtx_refdownval (run, lv);
 		return HAWK_NULL;
@@ -5613,7 +5613,7 @@ static hawk_val_t* eval_binop_nm (hawk_rtx_t* run, hawk_nde_t* left, hawk_nde_t*
 
 	hawk_rtx_refupval (run, rv);
 
-	res = eval_binop_match0 (run, lv, rv, &left->loc, &right->loc, 0);
+	res = eval_binop_match0(run, lv, rv, &left->loc, &right->loc, 0);
 
 	hawk_rtx_refdownval (run, rv);
 	hawk_rtx_refdownval (run, lv);
@@ -5640,19 +5640,19 @@ static hawk_val_t* eval_unary (hawk_rtx_t* rtx, hawk_nde_t* nde)
 		exp->opcode == HAWK_UNROP_BNOT);
 
 	HAWK_ASSERT (exp->left->next == HAWK_NULL);
-	left = eval_expression (rtx, exp->left);
-	if (left == HAWK_NULL) return HAWK_NULL;
+	left = eval_expression(rtx, exp->left);
+	if (HAWK_UNLIKELY(!left)) return HAWK_NULL;
 
 	hawk_rtx_refupval (rtx, left);
 
 	switch (exp->opcode)
 	{
 		case HAWK_UNROP_MINUS:
-			n = hawk_rtx_valtonum (rtx, left, &l, &r);
-			if (n <= -1) goto exit_func;
+			n = hawk_rtx_valtonum(rtx, left, &l, &r);
+			if (HAWK_UNLIKELY(n <= -1)) goto exit_func;
 
-			res = (n == 0)? hawk_rtx_makeintval (rtx, -l):
-			                hawk_rtx_makefltval (rtx, -r);
+			res = (n == 0)? hawk_rtx_makeintval(rtx, -l):
+			                hawk_rtx_makefltval(rtx, -r);
 			break;
 
 		case HAWK_UNROP_LNOT:
@@ -5660,38 +5660,37 @@ static hawk_val_t* eval_unary (hawk_rtx_t* rtx, hawk_nde_t* nde)
 			{
 				/* 0 if the string length is greater than 0.
 				 * 1 if it's empty */
-				res = hawk_rtx_makeintval (
-					rtx, !(((hawk_val_str_t*)left)->val.len > 0));
+				res = hawk_rtx_makeintval(rtx, !(((hawk_val_str_t*)left)->val.len > 0));
 			}
 			else
 			{
-				n = hawk_rtx_valtonum (rtx, left, &l, &r);
-				if (n <= -1) goto exit_func;
+				n = hawk_rtx_valtonum(rtx, left, &l, &r);
+				if (HAWK_UNLIKELY(n <= -1)) goto exit_func;
 
-				res = (n == 0)? hawk_rtx_makeintval (rtx, !l):
-				                hawk_rtx_makefltval (rtx, !r);
+				res = (n == 0)? hawk_rtx_makeintval(rtx, !l):
+				                hawk_rtx_makefltval(rtx, !r);
 			}
 			break;
-	
-		case HAWK_UNROP_BNOT:
-			n = hawk_rtx_valtoint (rtx, left, &l);
-			if (n <= -1) goto exit_func;
 
-			res = hawk_rtx_makeintval (rtx, ~l);
+		case HAWK_UNROP_BNOT:
+			n = hawk_rtx_valtoint(rtx, left, &l);
+			if (HAWK_UNLIKELY(n <= -1)) goto exit_func;
+
+			res = hawk_rtx_makeintval(rtx, ~l);
 			break;
 
 		case HAWK_UNROP_PLUS:
-			n = hawk_rtx_valtonum (rtx, left, &l, &r);
-			if (n <= -1) goto exit_func;
+			n = hawk_rtx_valtonum(rtx, left, &l, &r);
+			if (HAWK_UNLIKELY(n <= -1)) goto exit_func;
 
-			res = (n == 0)? hawk_rtx_makeintval (rtx, l):
-			                hawk_rtx_makefltval (rtx, r);
+			res = (n == 0)? hawk_rtx_makeintval(rtx, l):
+			                hawk_rtx_makefltval(rtx, r);
 			break;
 	}
 
 exit_func:
 	hawk_rtx_refdownval (rtx, left);
-	if (res == HAWK_NULL) ADJERR_LOC (rtx, &nde->loc);
+	if (HAWK_UNLIKELY(!res)) ADJERR_LOC (rtx, &nde->loc);
 	return res;
 }
 
@@ -5735,19 +5734,19 @@ static hawk_val_t* eval_incpre (hawk_rtx_t* rtx, hawk_nde_t* nde)
 	}
 
 	HAWK_ASSERT (exp->left->next == HAWK_NULL);
-	left = eval_expression (rtx, exp->left);
-	if (left == HAWK_NULL) return HAWK_NULL;
+	left = eval_expression(rtx, exp->left);
+	if (HAWK_UNLIKELY(!left)) return HAWK_NULL;
 
 	hawk_rtx_refupval (rtx, left);
-	left_vtype = HAWK_RTX_GETVALTYPE (rtx, left);
+	left_vtype = HAWK_RTX_GETVALTYPE(rtx, left);
 
 	switch (left_vtype)
 	{
 		case HAWK_VAL_INT:
 		{
 			hawk_int_t r = HAWK_RTX_GETINTFROMVAL (rtx, left);
-			res = hawk_rtx_makeintval (rtx, r + inc_val_int);
-			if (res == HAWK_NULL) 
+			res = hawk_rtx_makeintval(rtx, r + inc_val_int);
+			if (HAWK_UNLIKELY(!res))
 			{
 				hawk_rtx_refdownval (rtx, left);
 				ADJERR_LOC (rtx, &nde->loc);
@@ -5759,8 +5758,8 @@ static hawk_val_t* eval_incpre (hawk_rtx_t* rtx, hawk_nde_t* nde)
 		case HAWK_VAL_FLT:
 		{
 			hawk_flt_t r = ((hawk_val_flt_t*)left)->val;
-			res = hawk_rtx_makefltval (rtx, r + inc_val_flt);
-			if (res == HAWK_NULL) 
+			res = hawk_rtx_makefltval(rtx, r + inc_val_flt);
+			if (HAWK_UNLIKELY(!res))
 			{
 				hawk_rtx_refdownval (rtx, left);
 				ADJERR_LOC (rtx, &nde->loc);
@@ -5775,8 +5774,8 @@ static hawk_val_t* eval_incpre (hawk_rtx_t* rtx, hawk_nde_t* nde)
 			hawk_flt_t v2;
 			int n;
 
-			n = hawk_rtx_valtonum (rtx, left, &v1, &v2);
-			if (n <= -1)
+			n = hawk_rtx_valtonum(rtx, left, &v1, &v2);
+			if (HAWK_UNLIKELY(n <= -1))
 			{
 				hawk_rtx_refdownval (rtx, left);
 				ADJERR_LOC (rtx, &nde->loc);
@@ -5793,7 +5792,7 @@ static hawk_val_t* eval_incpre (hawk_rtx_t* rtx, hawk_nde_t* nde)
 				res = hawk_rtx_makefltval (rtx, v2 + inc_val_flt);
 			}
 
-			if (res == HAWK_NULL) 
+			if (HAWK_UNLIKELY(!res))
 			{
 				hawk_rtx_refdownval (rtx, left);
 				ADJERR_LOC (rtx, &nde->loc);
@@ -5804,7 +5803,7 @@ static hawk_val_t* eval_incpre (hawk_rtx_t* rtx, hawk_nde_t* nde)
 		}
 	}
 
-	if (do_assignment (rtx, exp->left, res) == HAWK_NULL)
+	if (HAWK_UNLIKELY(do_assignment(rtx, exp->left, res) == HAWK_NULL))
 	{
 		hawk_rtx_refdownval (rtx, left);
 		return HAWK_NULL;
@@ -5854,8 +5853,8 @@ static hawk_val_t* eval_incpst (hawk_rtx_t* rtx, hawk_nde_t* nde)
 	}
 
 	HAWK_ASSERT (exp->left->next == HAWK_NULL);
-	left = eval_expression (rtx, exp->left);
-	if (left == HAWK_NULL) return HAWK_NULL;
+	left = eval_expression(rtx, exp->left);
+	if (HAWK_UNLIKELY(!left)) return HAWK_NULL;
 
 	hawk_rtx_refupval (rtx, left);
 
@@ -5865,20 +5864,20 @@ static hawk_val_t* eval_incpst (hawk_rtx_t* rtx, hawk_nde_t* nde)
 	{
 		case HAWK_VAL_INT:
 		{
-			hawk_int_t r = HAWK_RTX_GETINTFROMVAL (rtx, left);
-			res = hawk_rtx_makeintval (rtx, r);
-			if (res == HAWK_NULL) 
+			hawk_int_t r = HAWK_RTX_GETINTFROMVAL(rtx, left);
+			res = hawk_rtx_makeintval(rtx, r);
+			if (HAWK_UNLIKELY(!res))
 			{
 				hawk_rtx_refdownval (rtx, left);
 				ADJERR_LOC (rtx, &nde->loc);
 				return HAWK_NULL;
 			}
 
-			res2 = hawk_rtx_makeintval (rtx, r + inc_val_int);
-			if (res2 == HAWK_NULL)
+			res2 = hawk_rtx_makeintval(rtx, r + inc_val_int);
+			if (HAWK_UNLIKELY(!res2))
 			{
 				hawk_rtx_refdownval (rtx, left);
-				hawk_rtx_freeval (rtx, res, 1);
+				hawk_rtx_freeval (rtx, res, HAWK_RTX_FREEVAL_CACHE);
 				ADJERR_LOC (rtx, &nde->loc);
 				return HAWK_NULL;
 			}
@@ -5889,19 +5888,19 @@ static hawk_val_t* eval_incpst (hawk_rtx_t* rtx, hawk_nde_t* nde)
 		case HAWK_VAL_FLT:
 		{
 			hawk_flt_t r = ((hawk_val_flt_t*)left)->val;
-			res = hawk_rtx_makefltval (rtx, r);
-			if (res == HAWK_NULL) 
+			res = hawk_rtx_makefltval(rtx, r);
+			if (HAWK_UNLIKELY(!res))
 			{
 				hawk_rtx_refdownval (rtx, left);
 				ADJERR_LOC (rtx, &nde->loc);
 				return HAWK_NULL;
 			}
 
-			res2 = hawk_rtx_makefltval (rtx, r + inc_val_flt);
-			if (res2 == HAWK_NULL)
+			res2 = hawk_rtx_makefltval(rtx, r + inc_val_flt);
+			if (HAWK_UNLIKELY(!res2))
 			{
 				hawk_rtx_refdownval (rtx, left);
-				hawk_rtx_freeval (rtx, res, 1);
+				hawk_rtx_freeval (rtx, res, HAWK_RTX_FREEVAL_CACHE);
 				ADJERR_LOC (rtx, &nde->loc);
 				return HAWK_NULL;
 			}
@@ -5915,8 +5914,8 @@ static hawk_val_t* eval_incpst (hawk_rtx_t* rtx, hawk_nde_t* nde)
 			hawk_flt_t v2;
 			int n;
 
-			n = hawk_rtx_valtonum (rtx, left, &v1, &v2);
-			if (n <= -1)
+			n = hawk_rtx_valtonum(rtx, left, &v1, &v2);
+			if (HAWK_UNLIKELY(n <= -1))
 			{
 				hawk_rtx_refdownval (rtx, left);
 				ADJERR_LOC (rtx, &nde->loc);
@@ -5925,19 +5924,19 @@ static hawk_val_t* eval_incpst (hawk_rtx_t* rtx, hawk_nde_t* nde)
 
 			if (n == 0) 
 			{
-				res = hawk_rtx_makeintval (rtx, v1);
-				if (res == HAWK_NULL)
+				res = hawk_rtx_makeintval(rtx, v1);
+				if (HAWK_UNLIKELY(!res))
 				{
 					hawk_rtx_refdownval (rtx, left);
 					ADJERR_LOC (rtx, &nde->loc);
 					return HAWK_NULL;
 				}
 
-				res2 = hawk_rtx_makeintval (rtx, v1 + inc_val_int);
-				if (res2 == HAWK_NULL)
+				res2 = hawk_rtx_makeintval(rtx, v1 + inc_val_int);
+				if (HAWK_UNLIKELY(!res2))
 				{
 					hawk_rtx_refdownval (rtx, left);
-					hawk_rtx_freeval (rtx, res, 1);
+					hawk_rtx_freeval (rtx, res, HAWK_RTX_FREEVAL_CACHE);
 					ADJERR_LOC (rtx, &nde->loc);
 					return HAWK_NULL;
 				}
@@ -5945,19 +5944,19 @@ static hawk_val_t* eval_incpst (hawk_rtx_t* rtx, hawk_nde_t* nde)
 			else /* if (n == 1) */
 			{
 				HAWK_ASSERT (n == 1);
-				res = hawk_rtx_makefltval (rtx, v2);
-				if (res == HAWK_NULL)
+				res = hawk_rtx_makefltval(rtx, v2);
+				if (HAWK_UNLIKELY(!res))
 				{
 					hawk_rtx_refdownval (rtx, left);
 					ADJERR_LOC (rtx, &nde->loc);
 					return HAWK_NULL;
 				}
 
-				res2 = hawk_rtx_makefltval (rtx, v2 + inc_val_flt);
-				if (res2 == HAWK_NULL)
+				res2 = hawk_rtx_makefltval(rtx, v2 + inc_val_flt);
+				if (HAWK_UNLIKELY(!res2))
 				{
 					hawk_rtx_refdownval (rtx, left);
-					hawk_rtx_freeval (rtx, res, 1);
+					hawk_rtx_freeval (rtx, res, HAWK_RTX_FREEVAL_CACHE);
 					ADJERR_LOC (rtx, &nde->loc);
 					return HAWK_NULL;
 				}
@@ -5967,7 +5966,7 @@ static hawk_val_t* eval_incpst (hawk_rtx_t* rtx, hawk_nde_t* nde)
 		}
 	}
 
-	if (do_assignment (rtx, exp->left, res2) == HAWK_NULL)
+	if (HAWK_UNLIKELY(do_assignment(rtx, exp->left, res2) == HAWK_NULL))
 	{
 		hawk_rtx_refdownval (rtx, left);
 		return HAWK_NULL;
diff --git a/hawk/lib/val-prv.h b/hawk/lib/val-prv.h
index 4db6daad..241aaff2 100644
--- a/hawk/lib/val-prv.h
+++ b/hawk/lib/val-prv.h
@@ -128,6 +128,10 @@ struct hawk_val_rchunk_t
 #define HAWK_VAL_ONE  HAWK_VTR_ONE
 #define HAWK_VAL_NEGONE HAWK_VTR_NEGONE
 
+
+#define HAWK_RTX_FREEVAL_CACHE       (1 << 0)
+#define HAWK_RTX_FREEVAL_GC_PRESERVE (1 << 1)
+
 #if defined(__cplusplus)
 extern "C" {
 #endif
@@ -142,7 +146,7 @@ extern hawk_val_t* hawk_val_zls;
 void hawk_rtx_freeval (
         hawk_rtx_t* rtx,
         hawk_val_t* val,
-        int         cache
+        int         flags
 );
 
 void hawk_rtx_freevalchunk (
diff --git a/hawk/lib/val.c b/hawk/lib/val.c
index b984c729..60b54c41 100644
--- a/hawk/lib/val.c
+++ b/hawk/lib/val.c
@@ -305,8 +305,7 @@ static void gc_free_unreachables (hawk_rtx_t* rtx, hawk_gch_t* list)
 	gch = list->gc_next;
 	while (gch != list)
 	{
-		/* -9999 preserves the outer shell */
-		hawk_rtx_freeval (rtx, hawk_gch_to_val(gch), -9999);
+		hawk_rtx_freeval (rtx, hawk_gch_to_val(gch), HAWK_RTX_FREEVAL_GC_PRESERVE);
 		gch = gch->gc_next;
 	}
 
@@ -318,7 +317,7 @@ static void gc_free_unreachables (hawk_rtx_t* rtx, hawk_gch_t* list)
 	#if defined(DEBUG_GC)
 		hawk_logbfmt (hawk_rtx_gethawk(rtx), HAWK_LOG_STDERR, "[GC] FREEING UNREACHABLE GCH %p gc_refs %zu v_refs %zu\n", gch, gch->gc_refs, hawk_gch_to_val(gch)->v_refs);
 	#endif
-		/* do what hawk_rtx_freeval() would do without -9999 */
+		/* do what hawk_rtx_freeval() would do without HAWK_RTX_FREEVAL_GC_PRESERVE */
 		rtx->gc.all_count--;
 		gc_unchain_gch (gch);
 		hawk_rtx_freemem (rtx, gch);
@@ -996,8 +995,8 @@ hawk_val_t* hawk_rtx_makemapvalwithdata (hawk_rtx_t* rtx, hawk_val_map_data_t da
 
 		if (tmp == HAWK_NULL || hawk_rtx_setmapvalfld(rtx, map, p->key.ptr, p->key.len, tmp) == HAWK_NULL)
 		{
-			if (tmp) hawk_rtx_freeval (rtx, tmp, 1);
-			hawk_rtx_freeval (rtx, map, 1);
+			if (tmp) hawk_rtx_freeval (rtx, tmp, HAWK_RTX_FREEVAL_CACHE);
+			hawk_rtx_freeval (rtx, map, HAWK_RTX_FREEVAL_CACHE);
 			return HAWK_NULL;
 		}
 	}
@@ -1126,7 +1125,7 @@ int hawk_rtx_getintfromval (hawk_rtx_t* rtx, hawk_val_t* val)
 	return HAWK_RTX_GETINTFROMVAL(rtx, val);
 }
 
-void hawk_rtx_freeval (hawk_rtx_t* rtx, hawk_val_t* val, int cache)
+void hawk_rtx_freeval (hawk_rtx_t* rtx, hawk_val_t* val, int flags)
 {
 	hawk_val_type_t vtype;
 
@@ -1164,7 +1163,7 @@ void hawk_rtx_freeval (hawk_rtx_t* rtx, hawk_val_t* val, int cache)
 			case HAWK_VAL_STR:
 			{
 			#if defined(HAWK_ENABLE_STR_CACHE)
-				if (cache)
+				if (flags & HAWK_RTX_FREEVAL_CACHE)
 				{
 					hawk_val_str_t* v = (hawk_val_str_t*)val;
 					hawk_oow_t aligned_len;
@@ -1189,7 +1188,7 @@ void hawk_rtx_freeval (hawk_rtx_t* rtx, hawk_val_t* val, int cache)
 
 			case HAWK_VAL_MBS:
 			#if defined(HAWK_ENABLE_MBS_CACHE)
-				if (cache)
+				if (flags & HAWK_RTX_FREEVAL_CACHE)
 				{
 					hawk_val_mbs_t* v = (hawk_val_mbs_t*)val;
 					hawk_oow_t aligned_len;
@@ -1233,11 +1232,11 @@ void hawk_rtx_freeval (hawk_rtx_t* rtx, hawk_val_t* val, int cache)
 			#if defined(HAWK_ENABLE_GC)
 
 				#if defined(DEBUG_GC)
-				hawk_logbfmt (hawk_rtx_gethawk(rtx), HAWK_LOG_STDERR, "[GC] FREEING GCH %p VAL %p - flags %d\n", hawk_val_to_gch(val), val, cache);
+				hawk_logbfmt (hawk_rtx_gethawk(rtx), HAWK_LOG_STDERR, "[GC] FREEING GCH %p VAL %p - flags %d\n", hawk_val_to_gch(val), val, flags);
 				#endif
 
 				hawk_map_fini (((hawk_val_map_t*)val)->map);
-				if (cache != -9999)
+				if (!(flags & HAWK_RTX_FREEVAL_GC_PRESERVE))
 				{
 					rtx->gc.all_count--;
 					gc_unchain_val (val);
@@ -1250,7 +1249,7 @@ void hawk_rtx_freeval (hawk_rtx_t* rtx, hawk_val_t* val, int cache)
 				break;
 
 			case HAWK_VAL_REF:
-				if (cache && rtx->rcache_count < HAWK_COUNTOF(rtx->rcache))
+				if ((flags & HAWK_RTX_FREEVAL_CACHE) && rtx->rcache_count < HAWK_COUNTOF(rtx->rcache))
 				{
 					rtx->rcache[rtx->rcache_count++] = (hawk_val_ref_t*)val;
 				}
@@ -1289,7 +1288,7 @@ void hawk_rtx_refdownval (hawk_rtx_t* rtx, hawk_val_t* val)
 		val->v_refs--;
 		if (val->v_refs <= 0) 
 		{
-			hawk_rtx_freeval(rtx, val, 1);
+			hawk_rtx_freeval (rtx, val, HAWK_RTX_FREEVAL_CACHE);
 		}
 	}
 }