diff --git a/bin/hcl.c b/bin/hcl.c
index 8f08fe4..9b08348 100644
--- a/bin/hcl.c
+++ b/bin/hcl.c
@@ -722,7 +722,7 @@ int main (int argc, char* argv[])
 	};
 	static hcl_bopt_t opt =
 	{
-		"l:bnv",
+		"l:nv",
 		lopt
 	};
 
@@ -730,7 +730,6 @@ int main (int argc, char* argv[])
 	hcl_oow_t heapsize = DEFAULT_HEAPSIZE;
 	int verbose = 0;
 	int show_info = 0;
-	int enable_block = 0;
 	int nl_terminator = 0;
 	const char* modlibdirs = HCL_NULL;
 
@@ -746,7 +745,6 @@ int main (int argc, char* argv[])
 	print_usage:
 		fprintf (stderr, "Usage: %s [options] script-filename [output-filename]\n", argv[0]);
 		fprintf (stderr, "Options are:\n");
-		fprintf (stderr, " -b  enable block construct with {}\n");
 		fprintf (stderr, " -n  enable line-break as expression terminator\n");
 		return -1;
 	}
@@ -759,10 +757,6 @@ int main (int argc, char* argv[])
 				logopt = opt.arg;
 				break;
 
-			case 'b':
-				enable_block = 1;
-				break;
-
 			case 'n':
 				nl_terminator = 1;
 				break;
@@ -838,10 +832,8 @@ int main (int argc, char* argv[])
 		/*trait |= HCL_TRAIT_NOGC;*/
 		trait |= HCL_TRAIT_AWAIT_PROCS;
 	#if 0
-		if (enable_block) trait |= HCL_TRAIT_LANG_ENABLE_BLOCK;
 		if (nl_terminator) trait |= HCL_TRAIT_LANG_ENABLE_EOL;
 	#else
-		trait |= HCL_TRAIT_LANG_ENABLE_BLOCK;
 		trait |= HCL_TRAIT_LANG_ENABLE_EOL;
 	#endif
 		hcl_setoption (hcl, HCL_TRAIT, &trait);
diff --git a/go/hcl.go b/go/hcl.go
index 7e570f1..65de131 100644
--- a/go/hcl.go
+++ b/go/hcl.go
@@ -67,7 +67,6 @@ type Ext struct {
 
 type BitMask C.hcl_bitmask_t
 
-const TRAIT_LANG_ENABLE_BLOCK BitMask = C.HCL_TRAIT_LANG_ENABLE_BLOCK
 const TRAIT_LANG_ENABLE_EOL BitMask = C.HCL_TRAIT_LANG_ENABLE_EOL
 
 var inst_table InstanceTable
diff --git a/lib/comp.c b/lib/comp.c
index 08a90ca..b35e729 100644
--- a/lib/comp.c
+++ b/lib/comp.c
@@ -28,9 +28,10 @@
  * no variable declaration if not enclosed in parentheses */
 #define LANG_LIMIT_DO
 
-#define FOR_NONE (0)
-#define FOR_IF   (1)
-#define FOR_TRY  (2)
+#define FOR_NONE  (0)
+#define FOR_IF    (1)
+#define FOR_TRY   (2)
+#define FOR_CLASS (3)
 
 enum
 {
@@ -469,8 +470,6 @@ static int check_block_expression_as_body (hcl_t* hcl, hcl_cnode_t* c, const hcl
 	car = HCL_CNODE_CONS_CAR(c);
 	if (!car || (HCL_CNODE_IS_CONS_CONCODED(car, HCL_CONCODE_VLIST) ||
 	             HCL_CNODE_IS_ELIST_CONCODED(car, HCL_CONCODE_VLIST)))
-	             /*(!HCL_CNODE_IS_CONS_CONCODED(car, HCL_CONCODE_BLOCK) &&
-	              !HCL_CNODE_IS_ELIST_CONCODED(car, HCL_CONCODE_BLOCK)))*/
 	{
 	no_block:
 		hcl_setsynerrbfmt (
@@ -480,6 +479,13 @@ static int check_block_expression_as_body (hcl_t* hcl, hcl_cnode_t* c, const hcl
 		return -1;
 	}
 
+	if (for_what == FOR_CLASS)
+	{
+		/* the class body must be enclosed in { .. }. e.g class X { ... } */
+		if (!HCL_CNODE_IS_CONS_CONCODED(car, HCL_CONCODE_BLOCK) &&
+		    !HCL_CNODE_IS_ELIST_CONCODED(car, HCL_CONCODE_BLOCK)) goto no_block;
+	}
+
 	/* there are special words that can't start a new expression */
 	if (HCL_CNODE_IS_SYMBOL_SYNCODED(car, HCL_SYNCODE_ELIF) ||
 	    HCL_CNODE_IS_SYMBOL_SYNCODED(car, HCL_SYNCODE_ELSE) ||
@@ -2331,10 +2337,7 @@ static HCL_INLINE int compile_else (hcl_t* hcl)
 		return -1;
 	}
 
-	if (hcl->option.trait & HCL_TRAIT_LANG_ENABLE_BLOCK)
-	{
-		if (check_block_expression_as_body(hcl, obj, cmd, FOR_NONE) <= -1) return -1;
-	}
+	if (check_block_expression_as_body(hcl, obj, cmd, FOR_NONE) <= -1) return -1;
 
 	SWITCH_TOP_CFRAME (hcl, COP_COMPILE_OBJECT_LIST, obj);
 
@@ -2381,7 +2384,7 @@ static int compile_class (hcl_t* hcl, hcl_cnode_t* src, int defclass)
 
 	if (defclass)
 	{
-		/* defun must be followed by an explicit function name */
+		/* defclass must be followed by an explicit class name */
 		HCL_ASSERT (hcl, HCL_CNODE_IS_SYMBOL_SYNCODED(cmd, HCL_SYNCODE_DEFCLASS));
 
 	class_as_defclass:
@@ -2426,16 +2429,9 @@ static int compile_class (hcl_t* hcl, hcl_cnode_t* src, int defclass)
 			class_name = HCL_CNODE_CONS_CAR(obj);
 			if (HCL_CNODE_IS_SYMBOL(class_name))
 			{
-			#if 0
-				hcl_setsynerrbfmt (
-					hcl, HCL_SYNERR_BANNEDVARNAME, HCL_CNODE_GET_LOC(class_name), HCL_CNODE_GET_TOK(class_name),
-					"class name not allowed in %.*js", HCL_CNODE_GET_TOKLEN(cmd), HCL_CNODE_GET_TOKPTR(cmd));
-				return -1;
-			#else
 				/* to handle 'class' in place of 'defclass' */
 				defclass = 1;
 				goto class_as_defclass;
-			#endif
 			}
 		}
 
@@ -2447,7 +2443,7 @@ static int compile_class (hcl_t* hcl, hcl_cnode_t* src, int defclass)
 		hcl_cnode_t* tmp, * dcl;
 
 		tmp = HCL_CNODE_CONS_CAR(obj);
-		if (!HCL_CNODE_IS_DBLCOLONS(tmp)) goto no_superclass;
+		if (/*!HCL_CNODE_IS_COLON(tmp)*/!HCL_CNODE_IS_DBLCOLONS(tmp)) goto no_superclass;
 
 		tmp = obj;
 		obj = HCL_CNODE_CONS_CDR(obj);
@@ -2537,7 +2533,7 @@ static HCL_INLINE int compile_class_p1 (hcl_t* hcl)
  )
 */
 		tmp = HCL_CNODE_CONS_CAR(obj);
-		if (HCL_CNODE_IS_DBLCOLONS(tmp))
+		if (/*HCL_CNODE_IS_COLON(tmp)|| */ HCL_CNODE_IS_DBLCOLONS(tmp))
 		{
 			/* class variables */
 			hcl_oow_t checkpoint;
@@ -2545,14 +2541,14 @@ static HCL_INLINE int compile_class_p1 (hcl_t* hcl)
 			obj = HCL_CNODE_CONS_CDR(obj);
 			if (!obj || !HCL_CNODE_IS_CONS(obj))
 			{
-				hcl_setsynerrbfmt (hcl, HCL_SYNERR_EOX, HCL_CNODE_GET_LOC(tmp), HCL_NULL, "no expression or declaration after triple colons");
+				hcl_setsynerrbfmt (hcl, HCL_SYNERR_EOX, HCL_CNODE_GET_LOC(tmp), HCL_NULL, "no expression or declaration after colon");
 				return -1;
 			}
 
 			tmp = HCL_CNODE_CONS_CAR(obj);
 			if (!HCL_CNODE_IS_CONS_CONCODED(tmp, HCL_CONCODE_VLIST))
 			{
-				hcl_setsynerrbfmt (hcl, HCL_SYNERR_EOX, HCL_CNODE_GET_LOC(tmp), HCL_NULL, "no declaration after triple colons");
+				hcl_setsynerrbfmt (hcl, HCL_SYNERR_EOX, HCL_CNODE_GET_LOC(tmp), HCL_NULL, "no declaration after colon");
 				return -1;
 			}
 
@@ -2624,10 +2620,7 @@ static HCL_INLINE int compile_class_p1 (hcl_t* hcl)
 		if (emit_push_literal(hcl, tmp, &cf->u._class.start_loc) <= -1) goto oops;
 	}
 
-	if (hcl->option.trait & HCL_TRAIT_LANG_ENABLE_BLOCK)
-	{
-		if (check_block_expression_as_body(hcl, obj, cf->u._class.cmd_cnode, FOR_NONE) <= -1) return -1;
-	}
+	if (check_block_expression_as_body(hcl, obj, cf->u._class.cmd_cnode, FOR_CLASS) <= -1) return -1;
 
 	if (push_clsblk(hcl, &cf->u._class.start_loc, nivars, ncvars, &hcl->c->tv.s.ptr[ivar_start], ivar_len, &hcl->c->tv.s.ptr[cvar_start], cvar_len) <= -1) goto oops;
 	if (push_cblk(hcl, &cf->u._class.start_loc, HCL_CBLK_TYPE_CLASS) <= -1) goto oops; /* the class block shall be treated as a control block, too */
@@ -3049,34 +3042,20 @@ static int compile_lambda (hcl_t* hcl, hcl_cnode_t* src, int defun)
 	}
 	HCL_ASSERT (hcl, nargs + nrvars == hcl->c->tv.wcount - saved_tv_wcount);
 
-	if (hcl->option.trait & HCL_TRAIT_LANG_ENABLE_BLOCK)
-	{
-		/*
-		 * defun aa(a b) { ...	};
-		 * (defun aa(a b) { ... })
-		 *
-		 * the block expression must be the first and the only expression at the body position.
-		 * the variable declaration can't be placed before the block expression.
-		 * it is supported inside the block expression itself.
-		 */
-		hcl_cnode_t* blk;
-		blk = HCL_CNODE_CONS_CDR(obj);
-		if (check_block_expression_as_body(hcl, blk, cmd, FOR_NONE) <= -1) return -1;
-		obj = blk;
-		nlvars = 0; /* no known local variables until the actual block is processed */
-	}
-	else
-	{
-		obj = HCL_CNODE_CONS_CDR(obj);
-		tv_dup_start = hcl->c->tv.s.len;
-		if (collect_vardcls(hcl, obj, &obj, tv_dup_start, &nlvars, "local") <= -1) return -1;
 
-		if (nlvars > MAX_CODE_NBLKLVARS)
-		{
-			hcl_setsynerrbfmt (hcl, HCL_SYNERR_VARFLOOD, HCL_CNODE_GET_LOC(args), HCL_NULL, "too many(%zu) variables in %.*js", nlvars, HCL_CNODE_GET_TOKLEN(cmd), HCL_CNODE_GET_TOKPTR(cmd));
-			return -1;
-		}
-	}
+	/*
+	 * defun aa(a b) { ...	};
+	 * (defun aa(a b) { ... })
+	 *
+	 * the block expression must be the first and the only expression at the body position.
+	 * the variable declaration can't be placed before the block expression.
+	 * it is supported inside the block expression itself.
+	 */
+	hcl_cnode_t* blk;
+	blk = HCL_CNODE_CONS_CDR(obj);
+	if (check_block_expression_as_body(hcl, blk, cmd, FOR_NONE) <= -1) return -1;
+	obj = blk;
+	nlvars = 0; /* no known local variables until the actual block is processed */
 
 	HCL_ASSERT (hcl, nargs + nrvars + nlvars == hcl->c->tv.wcount - saved_tv_wcount);
 
@@ -3468,10 +3447,7 @@ static int compile_try (hcl_t* hcl, hcl_cnode_t* src)
 	jump_inst_pos = hcl->code.bc.len;
 	if (emit_single_param_instruction(hcl, HCL_CODE_TRY_ENTER, MAX_CODE_JUMP, HCL_CNODE_GET_LOC(cmd)) <= -1) return -1;
 
-	if (hcl->option.trait & HCL_TRAIT_LANG_ENABLE_BLOCK)
-	{
-		if (check_block_expression_as_body(hcl, obj, cmd, FOR_TRY) <= -1) return -1;
-	}
+	if (check_block_expression_as_body(hcl, obj, cmd, FOR_TRY) <= -1) return -1;
 
 	SWITCH_TOP_CFRAME (hcl, COP_COMPILE_TRY_OBJECT_LIST, obj);  /* 1*/
 	PUSH_SUBCFRAME (hcl, COP_POST_TRY, cmd); /* 2 */
@@ -3598,10 +3574,7 @@ static HCL_INLINE int compile_catch (hcl_t* hcl)
 	HCL_ASSERT (hcl, fbi->tmpr_nargs + fbi->tmpr_nrvars + fbi->tmpr_nlvars == fbi->tmprcnt - par_tmprcnt);
 
 	obj = HCL_CNODE_CONS_CDR(obj);
-	if (hcl->option.trait & HCL_TRAIT_LANG_ENABLE_BLOCK)
-	{
-		if (check_block_expression_as_body(hcl, obj, cmd, FOR_NONE) <= -1) return -1;
-	}
+	if (check_block_expression_as_body(hcl, obj, cmd, FOR_NONE) <= -1) return -1;
 
 	/* jump_inst_pos hold the instruction pointer that skips the catch block at the end of the try block */
 	patch_nearest_post_try (hcl, &jump_inst_pos);
@@ -3748,10 +3721,7 @@ static int compile_while (hcl_t* hcl, hcl_cnode_t* src, int next_cop)
 	cond = HCL_CNODE_CONS_CAR(obj);
 	body = HCL_CNODE_CONS_CDR(obj);
 
-	if (hcl->option.trait & HCL_TRAIT_LANG_ENABLE_BLOCK)
-	{
-		if (check_block_expression_as_body(hcl, body, cmd, FOR_NONE) <= -1) return -1;
-	}
+	if (check_block_expression_as_body(hcl, body, cmd, FOR_NONE) <= -1) return -1;
 
 	SWITCH_TOP_CFRAME (hcl, COP_COMPILE_OBJECT, cond); /* 1 */
 
@@ -4661,11 +4631,6 @@ redo:
 					break;
 
 				case HCL_CONCODE_BLOCK:
-					if (!(hcl->option.trait & HCL_TRAIT_LANG_ENABLE_BLOCK))
-					{
-						hcl_setsynerrbfmt (hcl, HCL_SYNERR_BLOCKBANNED, HCL_CNODE_GET_LOC(oprnd), HCL_NULL, "block expression disallowed");
-						return -1;
-					}
 					if (compile_cons_block_expression(hcl, oprnd) <= -1) return -1;
 					break;
 
@@ -4721,12 +4686,6 @@ redo:
 					return -1;
 
 				case HCL_CONCODE_BLOCK:
-					if (!(hcl->option.trait & HCL_TRAIT_LANG_ENABLE_BLOCK))
-					{
-						/* this is treated the same as HCL_CNODE_CONS with CONCODE BLOCK */
-						hcl_setsynerrbfmt (hcl, HCL_SYNERR_BLOCKBANNED, HCL_CNODE_GET_LOC(oprnd), HCL_NULL, "block expression disallowed");
-						return -1;
-					}
 					if (compile_cons_block_expression(hcl, oprnd) <= -1) return -1;
 					break;
 
@@ -5176,10 +5135,7 @@ static HCL_INLINE int post_if_cond (hcl_t* hcl)
 	HCL_ASSERT (hcl, hcl->code.bc.len < HCL_SMOOI_MAX);
 	body_pos = hcl->code.bc.len;
 
-	if (hcl->option.trait & HCL_TRAIT_LANG_ENABLE_BLOCK)
-	{
-		if (check_block_expression_as_body(hcl, cf->operand, cf->u.post_if.cmd_cnode, FOR_IF) <= -1) return -1;
-	}
+	if (check_block_expression_as_body(hcl, cf->operand, cf->u.post_if.cmd_cnode, FOR_IF) <= -1) return -1;
 
 	SWITCH_TOP_CFRAME (hcl, COP_COMPILE_IF_OBJECT_LIST, cf->operand); /* 1 */
 	PUSH_SUBCFRAME (hcl, COP_POST_IF_BODY, cf->operand); /* 2 */
diff --git a/lib/hcl.h b/lib/hcl.h
index dc68fae..6ec6814 100644
--- a/lib/hcl.h
+++ b/lib/hcl.h
@@ -236,9 +236,6 @@ enum hcl_trait_t
 
 	/* return EOL as a token */ /* TODO: make this pragma controllable */
 	HCL_TRAIT_LANG_ENABLE_EOL = (((hcl_bitmask_t)1) << 14),
-
-	/* enable block expression as mandatory argument to some expresions */
-	HCL_TRAIT_LANG_ENABLE_BLOCK = (((hcl_bitmask_t)1) << 15),
 };
 typedef enum hcl_trait_t hcl_trait_t;
 
@@ -1566,10 +1563,7 @@ enum hcl_compile_flag_t
 	HCL_COMPILE_CLEAR_CODE  = (1 << 0),
 
 	/* clear the top-level function block at the end of hcl_compile() */
-	HCL_COMPILE_CLEAR_FNBLK = (1 << 1),
-
-	/* enable the block {} mode */
-	HCL_COMPILE_ENABLE_BLOCK = (1 << 2) /*TODO: make this #pragma controllable */
+	HCL_COMPILE_CLEAR_FNBLK = (1 << 1)
 };
 typedef enum hcl_compile_flag_t hcl_compile_flag_t;
 #endif
diff --git a/lib/x-server.c b/lib/x-server.c
index 2ce6cd8..d10974c 100644
--- a/lib/x-server.c
+++ b/lib/x-server.c
@@ -1522,7 +1522,6 @@ static int init_worker_hcl (hcl_server_worker_t* worker)
 	if (server->cfg.trait & HCL_SERVER_TRAIT_DEBUG_GC) trait |= HCL_TRAIT_DEBUG_GC;
 	if (server->cfg.trait & HCL_SERVER_TRAIT_DEBUG_BIGINT) trait |= HCL_TRAIT_DEBUG_BIGINT;
 #endif
-	trait |= HCL_TRAIT_LANG_ENABLE_BLOCK;
 	trait |= HCL_TRAIT_LANG_ENABLE_EOL;
 	hcl_setoption (hcl, HCL_TRAIT, &trait);
 
diff --git a/main.go b/main.go
index c77f319..57b2913 100644
--- a/main.go
+++ b/main.go
@@ -80,7 +80,7 @@ func main() {
 		x.SetLogTarget("/dev/stderr")
 	}
 
-	x.SetTrait(x.GetTrait() | hcl.TRAIT_LANG_ENABLE_EOL | hcl.TRAIT_LANG_ENABLE_BLOCK)
+	x.SetTrait(x.GetTrait() | hcl.TRAIT_LANG_ENABLE_EOL)
 
 	err = x.Ignite(1000000)
 	if err != nil {
diff --git a/pas/hcl.pas b/pas/hcl.pas
index 6575ee8..63088e8 100644
--- a/pas/hcl.pas
+++ b/pas/hcl.pas
@@ -16,13 +16,11 @@ type
 	BitMask = longword; (* this must match hcl_bitmask_t in hcl.h *)
 
 (*const
-	TRAIT_LANG_ENABLE_EOF = (BitMask(1) shl 14);
-	TRAIT_LANG_ENABLE_BLOCK = (BitMask(1) shl 15);*)
+	TRAIT_LANG_ENABLE_EOL = (BitMask(1) shl 14); *)
 
 type
 	TraitBit = ( (* this enum must follow hcl_trait_t in hcl.h *)
-		LANG_ENABLE_EOF = (BitMask(1) shl 14),
-		LANG_ENABLE_BLOCK = (BitMask(1) shl 15)
+		LANG_ENABLE_EOL = (BitMask(1) shl 14)
 	);
 
 	Option = ( (* this enum must follow hcl_option_t in hcl.h *)
@@ -171,8 +169,9 @@ begin
 		raise Exception.Create(errmsg);
 	end;
 
+	if hcl_getoption(h, Option.TRAIT, @tb) <= -1 then tb := 0;
 
-	tb := BitMask(TraitBit.LANG_ENABLE_EOF) or BitMask(TraitBit.LANG_ENABLE_BLOCK);
+	tb := tb or BitMask(TraitBit.LANG_ENABLE_EOL);
 	if hcl_setoption(h, Option.TRAIT, @tb) <= -1 then begin
 		hcl_errnum_to_errbcstr(errnum, @errmsg, length(errmsg));
 		hcl_close(h);
diff --git a/src/kernel.hcl b/src/kernel.hcl
index 037c331..355b339 100644
--- a/src/kernel.hcl
+++ b/src/kernel.hcl
@@ -1,7 +1,7 @@
 class Object {
 }
 
-class Collection: Object {
+class Collection : Object {
 }
 
 class IndexedCollection: Collection {
@@ -26,5 +26,22 @@ fun Collection:slice(index count) {
 
 
 
+class String: Array (a b c) {
+}
+
+class String: Array (
+	monaco
+	duncan
+	falcon
+	:deuce
+	:canival
+	:pebble
+	:godzilla
+) {
+	fun Collection:slice(index count) {
+		return (arr.slice self index count)
+	}
+}
+
 
 printf "string length %d\n" ("aaaa":length)
diff --git a/t/Makefile.am b/t/Makefile.am
index 37c8294..1d04131 100644
--- a/t/Makefile.am
+++ b/t/Makefile.am
@@ -32,8 +32,8 @@ TESTS = $(check_PROGRAMS) $(check_SCRIPTS) $(check_ERRORS)
 
 TEST_EXTENSIONS = .hcl .err
 
-HCL_LOG_COMPILER = $(SHELL) $(abs_srcdir)/run.sh ../bin/hcl --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0 -b -n
+HCL_LOG_COMPILER = $(SHELL) $(abs_srcdir)/run.sh ../bin/hcl --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0 -n
 AM_HCL_LOG_FLAGS =
 
-ERR_LOG_COMPILER = $(SHELL) $(abs_srcdir)/err.sh ../bin/hcl --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0 -b -n
+ERR_LOG_COMPILER = $(SHELL) $(abs_srcdir)/err.sh ../bin/hcl --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0 -n
 AM_ERR_LOG_FLAGS =
diff --git a/t/Makefile.in b/t/Makefile.in
index 47e8303..d84d018 100644
--- a/t/Makefile.in
+++ b/t/Makefile.in
@@ -497,9 +497,9 @@ check_ERRORS = \
 
 EXTRA_DIST = $(check_SCRIPTS) $(check_ERRORS)
 TEST_EXTENSIONS = .hcl .err
-HCL_LOG_COMPILER = $(SHELL) $(abs_srcdir)/run.sh ../bin/hcl --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0 -b -n
+HCL_LOG_COMPILER = $(SHELL) $(abs_srcdir)/run.sh ../bin/hcl --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0 -n
 AM_HCL_LOG_FLAGS = 
-ERR_LOG_COMPILER = $(SHELL) $(abs_srcdir)/err.sh ../bin/hcl --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0 -b -n
+ERR_LOG_COMPILER = $(SHELL) $(abs_srcdir)/err.sh ../bin/hcl --modlibdirs="@abs_top_builddir@/mod:@abs_top_builddir@/mod/.libs" --heapsize=0 -n
 AM_ERR_LOG_FLAGS = 
 all: all-am