diff --git a/lib/cnode.c b/lib/cnode.c
index fc8b41c..c366cdc 100644
--- a/lib/cnode.c
+++ b/lib/cnode.c
@@ -135,6 +135,11 @@ hak_cnode_t* hak_makecnodedsymbol (hak_t* hak, int flags, const hak_loc_t* loc,
 	return c;
 }
 
+hak_cnode_t* hak_makecnodebinop (hak_t* hak, int flags, const hak_loc_t* loc, const  hak_oocs_t* tok)
+{
+	return hak_makecnode(hak, HAK_CNODE_BINOP, flags, loc, tok);
+}
+
 hak_cnode_t* hak_makecnodestrlit (hak_t* hak, int flags, const hak_loc_t* loc, const hak_oocs_t* tok)
 {
 	return hak_makecnode(hak, HAK_CNODE_STRLIT, flags, loc, tok);
diff --git a/lib/comp.c b/lib/comp.c
index 640ae31..ab0b8b7 100644
--- a/lib/comp.c
+++ b/lib/comp.c
@@ -71,26 +71,25 @@ enum
 
 /* --------------------------------------------
 
+fun plus(x y) {
+	printf "plus %d %d\n" x y
+	fun minus(x y) {
+		printf "minus %d %d\n" x y
+		- x y
+	}
+	+ x y
+}
 
-(fun plus(x y)
-	(printf "plus %d %d\n" x y)
-	(fun minus(x y)
-		(printf "minus %d %d\n" x y)
-		(- x y)
-	)
-	(+ x y)
-)
+fun dummy(q) {
+	printf "%s\n" q
+}
 
-(fun dummy(q)
-	(printf "%s\n" q)
-)
+plus 10 20 ## minus is now available after plus is executed
+minus 10 1
 
-(plus 10 20)
-    <---- minus is now available
-(minus 10 1)
 literals -->
 //
-// characeter 'A'
+// character 'A'
 // "string"
 // B"byte string" <-- not yet implemented
 // array ---> #[   ] or [ ] ? constant or not?  dynamic???
@@ -459,7 +458,7 @@ HAK_INFO6(hak, "FOUND CLASS VAR [%.*js]...[%.*js]................ ===> ctx_offse
 				/* this condition indicates that the current function level contains a class defintion
 				 * and this variable is looked up inside the class defintion */
 HAK_INFO2(hak, "CLASS NAMED VAR [%.*js]\n", name->len, name->ptr);
-				vi->type = VAR_CLASS;//_NAMED; // TODO: create VAR_CLASS_NAMED???
+				vi->type = VAR_CLASS;/*_NAMED;*/ // TODO: create VAR_CLASS_NAMED???
 				vi->ctx_offset = 0;
 				vi->index_in_ctx = 0;
 			}
@@ -1546,7 +1545,7 @@ static int collect_vardcl_for_class (hak_t* hak, hak_cnode_t* obj, hak_cnode_t**
 			goto next;
 		}
 
-		if (!HAK_CNODE_IS_SYMBOL(var) || HAK_CNODE_IS_SYMBOL_BINOP(var)) goto synerr_varname;
+		if (!HAK_CNODE_IS_SYMBOL(var) /*|| HAK_CNODE_IS_SYMBOL_BINOP(var)*/) goto synerr_varname;
 
 		checkpoint = hak->c->tv.s.len;
 		n = add_temporary_variable(hak, var, tv_slen_saved, desc[enclosed], HAK_NULL);
@@ -1790,7 +1789,9 @@ enum
 	COP_EMIT_POP_INTO_CONS_CDR,
 
 	COP_EMIT_FUN,
+#if defined(USE_KW_PLUS)
 	COP_EMIT_PLUS,
+#endif
 	COP_EMIT_POP_STACKTOP,
 	COP_EMIT_RETURN,
 	COP_EMIT_SET,
@@ -2004,6 +2005,7 @@ static HAK_INLINE int compile_or_p2 (hak_t* hak)
 
 /* ========================================================================= */
 
+#if defined(USE_KW_PLUS)
 /* EXPERIMENT WITH BINOP */
 static int compile_plus (hak_t* hak, hak_cnode_t* src)
 {
@@ -2068,6 +2070,7 @@ static HAK_INLINE int emit_plus (hak_t* hak)
 	POP_CFRAME(hak);
 	return 0;
 }
+#endif
 
 /* ========================================================================= */
 
@@ -2819,7 +2822,7 @@ static int compile_class (hak_t* hak, hak_cnode_t* src)
 	check_class_name:
 		if (HAK_CNODE_IS_FOR_DATA_SIMPLE(tmp) || HAK_CNODE_IS_FOR_LANG(tmp))
 		{
-			if (!HAK_CNODE_IS_SYMBOL_IDENT(tmp))
+			if (!HAK_CNODE_IS_SYMBOL(tmp))
 			{
 				hak_setsynerrbfmt(
 					hak, HAK_SYNERR_CLASS, HAK_CNODE_GET_LOC(tmp), HAK_NULL,
@@ -3295,7 +3298,7 @@ static int compile_fun (hak_t* hak, hak_cnode_t* src)
 			tmp = HAK_CNODE_CONS_CAR(next);
 		}
 
-		if (HAK_CNODE_IS_SYMBOL(tmp))
+		if (HAK_CNODE_IS_SYMBOL(tmp) || HAK_CNODE_IS_BINOP(tmp))
 		{
 			/* 'fun' followed by name */
 		fun_got_name:
@@ -3332,7 +3335,7 @@ static int compile_fun (hak_t* hak, hak_cnode_t* src)
 				}
 
 				tmp = HAK_CNODE_CONS_CAR(next);
-				if (!HAK_CNODE_IS_SYMBOL(tmp))
+				if (!HAK_CNODE_IS_SYMBOL(tmp) && !HAK_CNODE_IS_BINOP(tmp))
 				{
 					hak_setsynerrbfmt(
 						hak, HAK_SYNERR_FUN, HAK_CNODE_GET_LOC(tmp), HAK_NULL,
@@ -3543,7 +3546,7 @@ static int compile_fun (hak_t* hak, hak_cnode_t* src)
 
 			if (in_ret_args)
 			{
-				if (!HAK_CNODE_IS_SYMBOL_IDENT(arg))
+				if (!HAK_CNODE_IS_SYMBOL(arg))
 				{
 					/* in 'fun x (x :: 20) { }', '20' is not a valid return variable name.
 					 * in 'fun x (x :: if) { }', 'if' is not a valid return variable name. */
@@ -3586,7 +3589,7 @@ static int compile_fun (hak_t* hak, hak_cnode_t* src)
 				{
 					va = 1;
 				}
-				else if (!HAK_CNODE_IS_SYMBOL_IDENT(arg))
+				else if (!HAK_CNODE_IS_SYMBOL(arg))
 				{
 					hak_setsynerrbfmt(
 						hak, HAK_SYNERR_ARGNAME, HAK_CNODE_GET_LOC(arg), HAK_NULL,
@@ -3615,6 +3618,18 @@ static int compile_fun (hak_t* hak, hak_cnode_t* src)
 		while (1);
 	}
 
+	if ((fun_type & 0xFF) == FUN_IM && fun_name && HAK_CNODE_IS_BINOP(fun_name) && (is_in_class_init_scope(hak) || class_name) && nargs != 1)
+	{
+		hak_setsynerrbfmt(
+			hak, HAK_SYNERR_ARGCOUNT, HAK_CNODE_GET_LOC(arg_list), HAK_NULL,
+			"only one argument expected for '%.*js%hs%.*js'",
+			(class_name? HAK_CNODE_GET_TOKLEN(class_name): 0),
+			(class_name? HAK_CNODE_GET_TOKPTR(class_name): HAK_NULL),
+			(class_name? ":": ""),
+			HAK_CNODE_GET_TOKLEN(fun_name), HAK_CNODE_GET_TOKPTR(fun_name));
+		return -1;
+	}
+
 	if (nargs > MAX_CODE_NBLKARGS) /*TODO: change this limit to max call argument count */
 	{
 		/* while an integer object is pused to indicate the number of
@@ -3860,7 +3875,7 @@ static int compile_var (hak_t* hak, hak_cnode_t* src)
 		tmp = HAK_CNODE_CONS_CAR(next);
 	}
 
-	if (HAK_CNODE_IS_SYMBOL_IDENT(tmp))
+	if (HAK_CNODE_IS_SYMBOL(tmp))
 	{
 		unsigned int var_type = VAR_INST;
 
@@ -3901,7 +3916,7 @@ static int compile_var (hak_t* hak, hak_cnode_t* src)
 			next = HAK_CNODE_CONS_CDR(next);
 			if (!next) break;
 			tmp = HAK_CNODE_CONS_CAR(next);
-			if (!HAK_CNODE_IS_SYMBOL_IDENT(tmp)) goto not_ident;
+			if (!HAK_CNODE_IS_SYMBOL(tmp)) goto not_ident;
 		}
 	}
 	else
@@ -4136,7 +4151,7 @@ static int compile_set_r (hak_t* hak, hak_cnode_t* src)
 	do
 	{
 		var = HAK_CNODE_CONS_CAR(obj);
-		if (!HAK_CNODE_IS_SYMBOL(var)) /* TODO: should this be HAK_CNODE_IS_SYMBOL(var)?? */
+		if (!HAK_CNODE_IS_SYMBOL(var))
 		{
 			if (nvars > 0) break;
 			hak_setsynerrbfmt(hak, HAK_SYNERR_VARNAME, HAK_CNODE_GET_LOC(var), HAK_CNODE_GET_TOK(var), "variable name not symbol in %.*js", HAK_CNODE_GET_TOKLEN(cmd), HAK_CNODE_GET_TOKPTR(cmd));
@@ -4883,9 +4898,11 @@ static int compile_cons_xlist_expression (hak_t* hak, hak_cnode_t* obj, int nret
 			if (compile_or(hak, obj) <= -1) return -1;
 			goto done;
 
+#if defined(USE_KW_PLUS)
 		case HAK_CNODE_PLUS:
 			if (compile_plus(hak, obj) <= -1) return -1;
 			goto done;
+#endif
 
 		case HAK_CNODE_SET:
 			if (compile_set(hak, obj) <= -1) return -1;
@@ -4896,7 +4913,9 @@ static int compile_cons_xlist_expression (hak_t* hak, hak_cnode_t* obj, int nret
 			goto done;
 	}
 
-	if (HAK_CNODE_IS_SYMBOL(car)  || HAK_CNODE_IS_DSYMBOL(car) ||
+	if (HAK_CNODE_IS_SYMBOL(car)  || HAK_CNODE_IS_DSYMBOL(car) || HAK_CNODE_IS_BINOP(car) ||
+	    HAK_CNODE_IS_STRLIT(car) || /* this condition to represent an external program TODO: change this to a dedicated cnode */
+	    HAK_CNODE_IS_SYMLIT(car) || /* this condition to represent an external program TODO: change this to a dedicated cnode */
 	    HAK_CNODE_IS_CONS_CONCODED(car, HAK_CONCODE_XLIST) ||
 	    HAK_CNODE_IS_CONS_CONCODED(car, HAK_CONCODE_MLIST) ||
 	    HAK_CNODE_IS_CONS_CONCODED(car, HAK_CONCODE_BLIST) ||
@@ -4947,7 +4966,7 @@ static int compile_cons_xlist_expression (hak_t* hak, hak_cnode_t* obj, int nret
 			}
 		}
 
-		if (HAK_CNODE_IS_SYMBOL(car) || HAK_CNODE_IS_DSYMBOL(car))
+		if (HAK_CNODE_IS_SYMBOL(car) || HAK_CNODE_IS_DSYMBOL(car) || HAK_CNODE_IS_BINOP(car))
 		{
 			hak_oop_cons_t sdc;
 
@@ -5038,14 +5057,34 @@ static int compile_cons_mlist_expression (hak_t* hak, hak_cnode_t* obj, hak_ooi_
 		return -1;
 	}
 	car = HAK_CNODE_CONS_CAR(cdr);
-	if (HAK_CNODE_IS_SYMBOL(car))
+	if (HAK_CNODE_IS_SYMBOL(car) || HAK_CNODE_IS_BINOP(car))
 	{
+		/* do not resolve the message itself to an associated value.
+		 * treat it as if it's a literal.
+		 * the actual message sending can be written with a symbol
+		 * as well as a symbol literal in that sense.
+		 *
+		 * For this class definition
+		 *   class X { fun[#ci] new() {} }
+		 * X:new is equivalent to X:#new
+		 *
+		 * If the method is a binop selector,
+		 *  class X { fun[#ci] +(a) {} } ## one argument is guaranteed by the reader
+		 * the followings are equivalent.
+		 *   X + 20
+		 *   X:#+ 20
+		 */
 		PUSH_CFRAME(hak, COP_EMIT_PUSH_SYMBOL, car);
 	}
+	else if (HAK_CNODE_IS_SYMLIT(car) || HAK_CNODE_IS_STRLIT(car))
+	{
+		PUSH_CFRAME(hak, COP_COMPILE_OBJECT, car);
+	}
 	else
 	{
-/* TODO: more sanity check on what can be used as a method */
-		PUSH_CFRAME(hak, COP_COMPILE_OBJECT, car);
+		hak_setsynerrbfmt(hak, HAK_SYNERR_MESSAGE, HAK_CNODE_GET_LOC(car), HAK_NULL,
+			"invalid message '%.*js'", HAK_CNODE_GET_TOKLEN(car), HAK_CNODE_GET_TOKPTR(car));
+		return -1;
 	}
 
 	/* compile <operand1> ... etc */
@@ -5071,31 +5110,6 @@ static int compile_cons_mlist_expression (hak_t* hak, hak_cnode_t* obj, hak_ooi_
 		}
 	}
 
-#if 0
-	if (HAK_CNODE_IS_SYMBOL(car) || HAK_CNODE_IS_DSYMBOL(car))
-	{
-		hak_oop_cons_t sdc;
-
-		/* only symbols are added to the system dictionary.
-		 * perform this lookup only if car is a symbol */
-		sdc = hak_lookupsysdicforsymbol_noseterr(hak, HAK_CNODE_GET_TOK(car));
-		if (sdc)
-		{
-			hak_oop_word_t sdv;
-			sdv = (hak_oop_word_t)HAK_CONS_CDR(sdc);
-			if (HAK_IS_PRIM(hak, sdv))
-			{
-				if (nargs < sdv->slot[1] || nargs > sdv->slot[2])
-				{
-					hak_setsynerrbfmt(hak, HAK_SYNERR_ARGCOUNT, HAK_CNODE_GET_LOC(car), HAK_NULL,
-						"parameters count(%zd) mismatch in function call - %.*js - expecting %zu-%zu parameters", nargs, HAK_CNODE_GET_TOKLEN(car), HAK_CNODE_GET_TOKPTR(car), sdv->slot[1], sdv->slot[2]);
-					return -1;
-				}
-			}
-		}
-	}
-#endif
-
 	/* redundant cdr check is performed inside compile_object_list() */
 	PUSH_SUBCFRAME(hak, COP_COMPILE_ARGUMENT_LIST, cdr);
 
@@ -5120,7 +5134,7 @@ static HAK_INLINE int compile_symbol (hak_t* hak, hak_cnode_t* obj)
 	hak_var_info_t vi;
 	int x;
 
-	HAK_ASSERT(hak, HAK_CNODE_IS_SYMBOL(obj));
+	HAK_ASSERT(hak, HAK_CNODE_IS_SYMBOL(obj) || HAK_CNODE_IS_BINOP(obj));
 
 	/* check if a symbol is a local variable */
 	x = find_variable_backward_with_token(hak, obj, &vi);
@@ -5598,6 +5612,7 @@ redo:
 			lit = HAK_ERROR_TO_OOP(oprnd->u.errlit.v);
 			goto literal;
 
+		case HAK_CNODE_BINOP: /* binop symbol. treat it like a normal symbol in the object context */
 		case HAK_CNODE_SYMBOL: /* symbol. but not a literal. usually a variable */
 			if (compile_symbol(hak, oprnd) <= -1) return -1;
 			goto done;
@@ -6626,7 +6641,7 @@ static HAK_INLINE int post_fun (hak_t* hak)
 		hak_var_info_t vi;
 		int x;
 
-		HAK_ASSERT(hak, HAK_CNODE_IS_SYMBOL(fun_name));
+		HAK_ASSERT(hak, HAK_CNODE_IS_SYMBOL(fun_name) || HAK_CNODE_IS_BINOP(fun_name));
 
 		if (is_in_class_init_scope(hak))
 		{
@@ -6804,7 +6819,7 @@ static HAK_INLINE int emit_set (hak_t* hak)
 		hak_oow_t index;
 		hak_oop_t cons, sym;
 
-		HAK_ASSERT(hak, HAK_CNODE_IS_SYMBOL(cf->operand));
+		HAK_ASSERT(hak, HAK_CNODE_IS_SYMBOL(cf->operand) || HAK_CNODE_IS_BINOP(cf->operand));
 
 		sym = hak_makesymbol(hak, HAK_CNODE_GET_TOKPTR(cf->operand), HAK_CNODE_GET_TOKLEN(cf->operand));
 		if (HAK_UNLIKELY(!sym)) return -1;
@@ -7171,9 +7186,11 @@ int hak_compile (hak_t* hak, hak_cnode_t* obj, int flags)
 				if (emit_fun(hak) <= -1) goto oops;
 				break;
 
+#if defined(USE_KW_PLUS)
 			case COP_EMIT_PLUS:
 				if (emit_plus(hak) <= -1) goto oops;
 				break;
+#endif
 
 			case COP_EMIT_POP_STACKTOP:
 				if (emit_pop_stacktop(hak) <= -1) goto oops;
diff --git a/lib/err.c b/lib/err.c
index d63695c..e3edd69 100644
--- a/lib/err.c
+++ b/lib/err.c
@@ -115,6 +115,7 @@ static const char* synerrstr[] =
 	"} expected",
 	"| expected",
 
+	"identifier expected",
 	"string expected",
 	"byte too small or too large",
 	"nesting level too deep",
@@ -161,6 +162,7 @@ static const char* synerrstr[] =
 	"break outside loop",
 
 	"invalid callable",
+	"invalid message",
 	"unbalanced key/value pair",
 	"unbalanced parenthesis/brace/bracket",
 	"unexpected semicolon",
diff --git a/lib/exec.c b/lib/exec.c
index 5e1a016..599ec3c 100644
--- a/lib/exec.c
+++ b/lib/exec.c
@@ -25,6 +25,8 @@
 
 #include "hak-prv.h"
 
+#define ENABLE_SYSCMD
+
 static const char* io_type_str[] =
 {
 	"input",
@@ -2145,23 +2147,23 @@ static HAK_INLINE int activate_function (hak_t* hak, hak_ooi_t nargs)
 /* ------------------------------------------------------------------------- */
 static HAK_INLINE int call_primitive (hak_t* hak, hak_ooi_t nargs)
 {
-	hak_oop_prim_t rcv;
+	hak_oop_prim_t op_prim;
 
-	rcv = (hak_oop_prim_t)HAK_STACK_GETOP(hak, nargs);
-	HAK_ASSERT(hak, HAK_IS_PRIM(hak, rcv));
-	HAK_ASSERT(hak, HAK_OBJ_GET_SIZE(rcv) == HAK_PRIM_NAMED_INSTVARS);
+	op_prim = (hak_oop_prim_t)HAK_STACK_GETOP(hak, nargs);
+	HAK_ASSERT(hak, HAK_IS_PRIM(hak, op_prim));
+	HAK_ASSERT(hak, HAK_OBJ_GET_SIZE(op_prim) == HAK_PRIM_NAMED_INSTVARS);
 
-	if (nargs < rcv->min_nargs && nargs > rcv->max_nargs)
+	if (nargs < op_prim->min_nargs && nargs > op_prim->max_nargs)
 	{
 /* TODO: include a primitive name... */
 		HAK_LOG3(hak, HAK_LOG_IC | HAK_LOG_ERROR,
 			"Error - wrong number of arguments to a primitive - expecting %zd-%zd, got %zd\n",
-			rcv->min_nargs, rcv->max_nargs, nargs);
+			op_prim->min_nargs, op_prim->max_nargs, nargs);
 		hak_seterrnum(hak, HAK_ECALLARG);
 		return -1;
 	}
 
-	return ((hak_pfimpl_t)rcv->impl)(hak, (hak_mod_t*)rcv->mod, nargs);
+	return ((hak_pfimpl_t)op_prim->impl)(hak, (hak_mod_t*)op_prim->mod, nargs);
 }
 
 /* ------------------------------------------------------------------------- */
@@ -2495,6 +2497,7 @@ static void supplement_errmsg (hak_t* hak, hak_ooi_t ip)
 		HAK_ASSERT(hak, HAK_IS_BYTEARRAY(hak, hak->active_function->dbgi));
 		dbgi = (hak_dbgi_t*)HAK_OBJ_GET_BYTE_SLOT(hak->active_function->dbgi);
 
+		orgloc.line = dbgi[ip].sline; /* update the line of the location at least */
 		hak_seterrbfmtloc(hak, orgnum, &orgloc, "%js (%js:%zu)", orgmsg,
 			(dbgi[ip].fname? dbgi[ip].fname: oocstr_dash), dbgi[ip].sline);
 
@@ -2515,7 +2518,7 @@ static int do_throw_with_internal_errmsg (hak_t* hak, hak_ooi_t ip)
 /* ------------------------------------------------------------------------- */
 
 
-#if 0
+#if defined(ENABLE_SYSCMD)
 /* EXPERIMENTAL CODE INTEGRATING EXTERNAL COMMANDS */
 
 #include <unistd.h>
@@ -2595,29 +2598,29 @@ done:
 
 static HAK_INLINE int exec_syscmd (hak_t* hak, hak_ooi_t nargs)
 {
-	hak_oop_word_t rcv;
+	hak_oop_word_t op_cmd;
 	hak_bch_t* cmd = HAK_NULL;
 	hak_bch_t* xcmd = HAK_NULL;
 
-	rcv = (hak_oop_word_t)HAK_STACK_GETOP(hak, nargs);
-	/*HAK_ASSERT(hak, HAK_IS_STRING(hak, rcv) || HAK_IS_SYMBOL(hak, rcv));*/
-	HAK_ASSERT(hak, HAK_OBJ_IS_CHAR_POINTER(rcv));
+	op_cmd = (hak_oop_word_t)HAK_STACK_GETOP(hak, nargs);
+	/*HAK_ASSERT(hak, HAK_IS_STRING(hak, op_cmd) || HAK_IS_SYMBOL(hak, op_cmd));*/
+	HAK_ASSERT(hak, HAK_OBJ_IS_CHAR_POINTER(op_cmd));
 
-	if (HAK_OBJ_GET_SIZE(rcv) == 0 || hak_count_oocstr(HAK_OBJ_GET_CHAR_SLOT(rcv)) != HAK_OBJ_GET_SIZE(rcv))
+	if (HAK_OBJ_GET_SIZE(op_cmd) == 0 || hak_count_oocstr(HAK_OBJ_GET_CHAR_SLOT(op_cmd)) != HAK_OBJ_GET_SIZE(op_cmd))
 	{
 		/* '\0' is contained in the middle */
-		hak_seterrbfmt(hak, HAK_EINVAL, "invalid callable %O", rcv);
+		hak_seterrbfmt(hak, HAK_EINVAL, "invalid callable %O", op_cmd);
 		goto oops;
 	}
 
-	cmd = hak_dupootobcstr(hak, HAK_OBJ_GET_CHAR_SLOT(rcv), HAK_NULL);
+	cmd = hak_dupootobcstr(hak, HAK_OBJ_GET_CHAR_SLOT(op_cmd), HAK_NULL);
 	if (!cmd) goto oops;
 
 	if (hak_find_bchar_in_bcstr(cmd, '/'))
 	{
 		if (!is_regular_executable_file_by_me(cmd))
 		{
-			hak_seterrbfmt(hak, HAK_ECALL, "cannot execute %O", rcv);
+			hak_seterrbfmt(hak, HAK_ECALL, "cannot execute %O", op_cmd);
 			goto oops;
 		}
 
@@ -3636,7 +3639,7 @@ static int execute (hak_t* hak)
 
 			/* ------------------------------------------------- */
 		#if 0
-			// the compiler never emits these instructions. reuse these instructions for other purposes
+			/* the compiler never emits these instructions. reuse these instructions for other purposes */
 			case HAK_CODE_PUSH_TEMPVAR_X:
 			case HAK_CODE_STORE_INTO_TEMPVAR_X:
 			case HAK_CODE_POP_INTO_TEMPVAR_X:
@@ -4007,6 +4010,17 @@ static int execute (hak_t* hak)
 							}
 							break;
 
+#if defined(ENABLE_SYSCMD)
+						case HAK_BRAND_STRING:
+						case HAK_BRAND_SYMBOL:
+							if (exec_syscmd(hak, b1) <= -1)
+							{
+								if (do_throw_with_internal_errmsg(hak, fetched_instruction_pointer) >= 0) break;
+								goto call_failed;
+							}
+							break;
+#endif
+
 						default:
 							goto cannot_call;
 					}
@@ -4786,7 +4800,7 @@ hak_logbfmt(hak, HAK_LOG_STDERR, ">>>%O c->sc=%O sc=%O b2=%d b3=%d nivars=%d ncv
 				t2 = HAK_STACK_GETTOP(hak); /* key */
 				HAK_STACK_POP(hak);
 				t3 = HAK_STACK_GETTOP(hak); /* dictionary */
-				if (!hak_putatdic(hak, (hak_oop_dic_t)t3, t2, t1)) goto oops;
+				if (!hak_putatdic(hak, (hak_oop_dic_t)t3, t2, t1)) goto oops_with_errmsg_supplement;
 				break;
 			}
 
@@ -4834,7 +4848,7 @@ hak_logbfmt(hak, HAK_LOG_STDERR, ">>>%O c->sc=%O sc=%O b2=%d b3=%d nivars=%d ncv
 					hak_pushvolat(hak, &t3);
 					t = hak_makecons(hak, t1, hak->_nil);
 					hak_popvolat(hak);
-					if (HAK_UNLIKELY(!t)) goto oops;
+					if (HAK_UNLIKELY(!t)) goto oops_with_errmsg_supplement;
 
 					((hak_oop_oop_t)t3)->slot[1] = t;
 					HAK_STACK_PUSH(hak, t);
@@ -4872,7 +4886,7 @@ hak_logbfmt(hak, HAK_LOG_STDERR, ">>>%O c->sc=%O sc=%O b2=%d b3=%d nivars=%d ncv
 					hak_pushvolat(hak, &t3);
 					t = hak_makecons(hak, t1, hak->_nil);
 					hak_popvolat(hak);
-					if (HAK_UNLIKELY(!t)) goto oops;
+					if (HAK_UNLIKELY(!t)) goto oops_with_errmsg_supplement;
 
 					((hak_oop_oop_t)t3)->slot[1] = t;
 				}
diff --git a/lib/gc.c b/lib/gc.c
index 2103318..0afd539 100644
--- a/lib/gc.c
+++ b/lib/gc.c
@@ -1045,7 +1045,7 @@ void hak_gc_ms_sweep_lazy (hak_t* hak, hak_oow_t allocsize)
 
 		if (HAK_OBJ_GET_FLAGS_MOVED(obj)) /* if marked */
 		{
-			HAK_OBJ_SET_FLAGS_MOVED (obj, 0); /* unmark */
+			HAK_OBJ_SET_FLAGS_MOVED(obj, 0); /* unmark */
 			prev = curr;
 		}
 		else
@@ -1380,15 +1380,15 @@ static hak_oop_class_t alloc_kernel_class (hak_t* hak, int class_flags, hak_oow_
 	c = (hak_oop_class_t)hak_allocoopobj(hak, HAK_CLASS_NAMED_INSTVARS + num_classvars);
 	if (HAK_UNLIKELY(!c)) return HAK_NULL;
 
-	HAK_OBJ_SET_FLAGS_KERNEL (c, HAK_OBJ_FLAGS_KERNEL_IMMATURE);
+	HAK_OBJ_SET_FLAGS_KERNEL(c, HAK_OBJ_FLAGS_KERNEL_IMMATURE);
 
 	cspec = kernel_classes[KCI_CLASS].class_spec_flags;
-	if (HAK_CLASS_SPEC_IS_IMMUTABLE(cspec)) HAK_OBJ_SET_FLAGS_RDONLY (c, 1); /* just for completeness of code. will never be true as it's not defined in the kernel class info table */
+	if (HAK_CLASS_SPEC_IS_IMMUTABLE(cspec)) HAK_OBJ_SET_FLAGS_RDONLY(c, 1); /* just for completeness of code. will never be true as it's not defined in the kernel class info table */
 #if 0 /* TODO extend the flags and uncomment this part */
-	if (HAK_CLASS_SPEC_IS_UNCOPYABLE(cspec)) HAK_OBJ_SET_FLAGS_UNCOPYABLE (c, 1); /* class itself is uncopyable */
+	if (HAK_CLASS_SPEC_IS_UNCOPYABLE(cspec)) HAK_OBJ_SET_FLAGS_UNCOPYABLE(c, 1); /* class itself is uncopyable */
 #endif
 
-	HAK_OBJ_SET_CLASS (c, (hak_oop_t)hak->c_class);
+	HAK_OBJ_SET_CLASS(c, (hak_oop_t)hak->c_class);
 	c->spec = HAK_SMOOI_TO_OOP(spec);
 	c->selfspec = HAK_SMOOI_TO_OOP(HAK_CLASS_SELFSPEC_MAKE(num_classvars, 0, class_flags));
 	c->nivars_super = HAK_SMOOI_TO_OOP(nivars_super); /* TODO: encode it into spec? */
diff --git a/lib/hak-prv.h b/lib/hak-prv.h
index 37bd998..5eb7084 100644
--- a/lib/hak-prv.h
+++ b/lib/hak-prv.h
@@ -326,7 +326,9 @@ enum hak_tok_type_t
 	HAK_TOK_REVERT,
 	HAK_TOK_AND,
 	HAK_TOK_OR,
+#if defined(USE_KW_PLUS)
 	HAK_TOK_PLUS,
+#endif
 	HAK_TOK_SET,
 	HAK_TOK_SET_R,
 
@@ -396,6 +398,7 @@ enum hak_cnode_type_t
 	HAK_CNODE_BCHRLIT,
 	HAK_CNODE_SYMBOL,
 	HAK_CNODE_DSYMBOL, /* dotted symbol */
+	HAK_CNODE_BINOP,
 	HAK_CNODE_STRLIT,
 	HAK_CNODE_BSTRLIT,
 	HAK_CNODE_SYMLIT,
@@ -439,7 +442,9 @@ enum hak_cnode_type_t
 	HAK_CNODE_REVERT,
 	HAK_CNODE_AND,
 	HAK_CNODE_OR,
+#if defined(USE_KW_PLUS)
 	HAK_CNODE_PLUS,
+#endif
 	HAK_CNODE_SET,
 	HAK_CNODE_SET_R,  /* language item for HAK_CODE_IS_FOR_LANG */
 
@@ -483,8 +488,9 @@ typedef enum hak_cnode_flag_t hak_cnode_flag_t;
 #define HAK_CNODE_IS_COLONLT(x) ((x)->cn_type == HAK_CNODE_COLONLT)
 
 #define HAK_CNODE_IS_SYMBOL(x) ((x)->cn_type == HAK_CNODE_SYMBOL)
-#define HAK_CNODE_IS_SYMBOL_IDENT(x) (HAK_CNODE_IS_SYMBOL(x) && !hak_is_binop_char((x)->cn_tok.ptr[0]))
-#define HAK_CNODE_IS_SYMBOL_BINOP(x) (HAK_CNODE_IS_SYMBOL(x) && hak_is_binop_char((x)->cn_tok.ptr[0]))
+#define HAK_CNODE_IS_BINOP(x) ((x)->cn_type == HAK_CNODE_BINOP)
+#define HAK_CNODE_IS_STRLIT(x) ((x)->cn_type == HAK_CNODE_STRLIT)
+#define HAK_CNODE_IS_SYMLIT(x) ((x)->cn_type == HAK_CNODE_SYMLIT)
 
 #define HAK_CNODE_IS_DSYMBOL(x) ((x)->cn_type == HAK_CNODE_DSYMBOL)
 #define HAK_CNODE_IS_DSYMBOL_CLA(x) ((x)->cn_type == HAK_CNODE_DSYMBOL && (x)->u.dsymbol.is_cla)
@@ -900,6 +906,7 @@ struct hak_frd_t
 {
 	int level;
 	int flagv;
+	int expect_pragma_item;
 	int expect_include_file;
 	int expect_vlist_item;
 	int do_include_file;
@@ -1357,6 +1364,7 @@ enum hak_bcode_t
 	HAK_CODE_PUSH_NEGINTLIT           = 0xB3, /* 179 */
 	HAK_CODE_PUSH_CHARLIT             = 0xB4, /* 180 */
 
+/* TODO: generalize it to support binops, not just plus */
 	HAK_CODE_PLUS = 0xB5, /* 181 TOOD: move it to a lower code number later after killing OBJVAR instructions */
 	/* UNUSED - 0xB6-0xB7 */
 
@@ -2022,6 +2030,7 @@ hak_cnode_t* hak_makecnodecharlit (hak_t* hak, int flags, const hak_loc_t* loc,
 hak_cnode_t* hak_makecnodebchrlit (hak_t* hak, int flags, const hak_loc_t* loc, const hak_oocs_t* tok, hak_oob_t v);
 hak_cnode_t* hak_makecnodesymbol (hak_t* hak, int flags, const hak_loc_t* loc, const hak_oocs_t* tok);
 hak_cnode_t* hak_makecnodedsymbol (hak_t* hak, int flags, const hak_loc_t* loc, const hak_oocs_t* tok, int is_cla);
+hak_cnode_t* hak_makecnodebinop (hak_t* hak, int flags, const hak_loc_t* loc, const hak_oocs_t* tok);
 hak_cnode_t* hak_makecnodestrlit (hak_t* hak, int flags, const hak_loc_t* loc, const hak_oocs_t* tok);
 hak_cnode_t* hak_makecnodebstrlit (hak_t* hak, int flags, const hak_loc_t* loc, const hak_oocs_t* tok);
 hak_cnode_t* hak_makecnodesymlit (hak_t* hak, int flags, const hak_loc_t* loc, const hak_oocs_t* tok);
diff --git a/lib/hak.h b/lib/hak.h
index abaf5f6..6566fad 100644
--- a/lib/hak.h
+++ b/lib/hak.h
@@ -119,6 +119,7 @@ enum hak_synerrnum_t
 	HAK_SYNERR_RBRACE,        /* } expected */
 	HAK_SYNERR_VBAR,          /* | expected */
 
+	HAK_SYNERR_IDENT,         /* identifier expected */
 	HAK_SYNERR_STRING,        /* string expected */
 	HAK_SYNERR_BYTERANGE,     /* byte too small or too large */
 	HAK_SYNERR_NESTING,       /* nesting level too deep */
@@ -165,6 +166,7 @@ enum hak_synerrnum_t
 	HAK_SYNERR_BREAK,         /* break outside loop */
 
 	HAK_SYNERR_CALLABLE,      /* invalid callable */
+	HAK_SYNERR_MESSAGE,       /* invalid message */
 	HAK_SYNERR_UNBALKV,       /* unbalanced key/value pair */
 	HAK_SYNERR_UNBALPBB,      /* unbalanced parenthesis/brace/bracket */
 	HAK_SYNERR_SEMICOLON,     /* unexpected semicolon */
diff --git a/lib/json.c b/lib/json.c
index 1ecf8c5..a171036 100644
--- a/lib/json.c
+++ b/lib/json.c
@@ -891,7 +891,7 @@ static int feed_json_data_u (hak_json_t* json, const hak_uch_t* data, hak_oow_t
 		hak_oow_t n, i;
 
 		n = json->_gem.cmgr->uctobc(*ptr++, bcsbuf, HAK_COUNTOF(bcsbuf));
-		if (n == 0) goto oops; // illegal character
+		if (n == 0) goto oops; /* illegal character */
 
 		for (i = 0; i < n; i++)
 		{
diff --git a/lib/print.c b/lib/print.c
index 0766b43..0325bd3 100644
--- a/lib/print.c
+++ b/lib/print.c
@@ -957,7 +957,9 @@ void hak_dumpcnode (hak_t* hak, hak_cnode_t* cnode, int newline)
 			case HAK_CNODE_REVERT:
 			case HAK_CNODE_AND:
 			case HAK_CNODE_OR:
+#if defined(USE_KW_PLUS)
 			case HAK_CNODE_PLUS:
+#endif
 			case HAK_CNODE_SET:
 			case HAK_CNODE_SET_R:
 
diff --git a/lib/read.c b/lib/read.c
index 7ad63d9..9afda41 100644
--- a/lib/read.c
+++ b/lib/read.c
@@ -76,7 +76,9 @@ static struct voca_t
 	{  6, { 'r','e','v','e','r','t'                                       } },
 	{  3, { 'a','n','d'                                                   } },
 	{  2, { 'o','r',                                                      } },
+#if defined(USE_KW_PLUS)
 	{  4, { 'p','l','u','s'                                               } },
+#endif
 	{  3, { 's','e','t'                                                   } },
 	{  5, { 's','e','t','-','r'                                           } },
 
@@ -137,7 +139,9 @@ enum voca_id_t
 	VOCA_KW_REVERT,
 	VOCA_KW_AND,
 	VOCA_KW_OR,
+#if defined(USE_KW_PLUS)
 	VOCA_KW_PLUS,
+#endif
 	VOCA_KW_SET,
 	VOCA_KW_SET_R,
 
@@ -285,7 +289,6 @@ static HAK_INLINE int is_delim_char (hak_ooci_t c)
 	       c == '#' || c == '\"' || c == '\'' || c == '\\' || is_spacechar(c) || c == HAK_OOCI_EOF;
 }
 
-
 int hak_is_binop_char (hak_ooci_t c) /* not static HAK_INLINE for shared use with comp.c via HAK_CNODE_IS_SYMBOL() */
 {
 	return c == '&' || c == '*' || c == '+' || c == '-' || c == '/' || c == '%' ||
@@ -293,9 +296,23 @@ int hak_is_binop_char (hak_ooci_t c) /* not static HAK_INLINE for shared use wit
 }
 #define is_binop_char(c) hak_is_binop_char(c)
 
+static HAK_INLINE int is_pure_lead_ident_char (hak_ooci_t c)
+{
+	return hak_is_ooch_alnum(c) || c == '_';
+}
+
+static HAK_INLINE int is_pure_ident_char (hak_ooci_t c)
+{
+	return hak_is_ooch_alnum(c) || c == '_' || c == '-';
+}
+
 static HAK_INLINE int is_lead_ident_char (hak_ooci_t c)
 {
+#if defined(STRICT_BINOP)
 	return hak_is_ooch_alpha(c) || c == '_';
+#else
+	return hak_is_ooch_alnum(c) || c == '_' || c == '-' || c == '?' || is_binop_char(c);
+#endif
 }
 
 static HAK_INLINE int is_ident_char (hak_ooci_t c)
@@ -304,7 +321,11 @@ static HAK_INLINE int is_ident_char (hak_ooci_t c)
 	 *  '-' is prohibited as the last character of an identifier or an identifier segment.
 	 *  see flx_plain_ident().
 	 */
+#if defined(STRICT_BINOP)
 	return hak_is_ooch_alnum(c) || c == '_' || c == '-' || c == '?';
+#else
+	return hak_is_ooch_alnum(c) || c == '_' || c == '-' || c == '?' || is_binop_char(c);
+#endif
 }
 
 /* TODO: remove GET_CHAR(), GET_CHAR_TO(), get_char(), _get_char() */
@@ -458,6 +479,7 @@ static int get_char (hak_t* hak)
 static hak_tok_type_t classify_ident_token (hak_t* hak, const hak_oocs_t* v)
 {
 	hak_oow_t i;
+	int is_binop;
 	static struct
 	{
 		int voca_id;
@@ -488,7 +510,9 @@ static hak_tok_type_t classify_ident_token (hak_t* hak, const hak_oocs_t* v)
 		{ VOCA_KW_REVERT,   HAK_TOK_REVERT   },
 		{ VOCA_KW_AND,      HAK_TOK_AND      },
 		{ VOCA_KW_OR,       HAK_TOK_OR       },
+#if defined(USE_KW_PLUS)
 		{ VOCA_KW_PLUS,     HAK_TOK_PLUS     },
+#endif
 		{ VOCA_KW_SET,      HAK_TOK_SET      },
 		{ VOCA_KW_SET_R,    HAK_TOK_SET_R    }
 	};
@@ -499,7 +523,44 @@ static hak_tok_type_t classify_ident_token (hak_t* hak, const hak_oocs_t* v)
 		if (hak_comp_oochars(v->ptr, v->len, vocas[vid].str, vocas[vid].len) == 0) return tab[i].type;
 	}
 
-	return HAK_TOK_IDENT;
+	if (is_pure_lead_ident_char(v->ptr[0]))
+	{
+		/* check if the word conforms to pure identifier rules:
+		 *  begins with alnum or _
+		 *  may contains a dash or dashes in between
+		 *  ends with alnum or _ or ?
+		 */
+		hak_oow_t wc = 1;
+		int q = 0;
+		for (i = 1; i < v->len; i++)
+		{
+			if (q && v->ptr[i] != '?') goto not_ident;
+
+			if (v->ptr[i] == '-')
+			{
+				/*if (wc == 0) goto not_ident;*/
+				wc = 0;
+			}
+			else if (v->ptr[i] == '?') q = 1;
+			else if (!is_pure_ident_char(v->ptr[i])) goto not_ident;
+			else wc++;
+		}
+
+		if (wc > 0) return HAK_TOK_IDENT;
+	}
+
+not_ident:
+	is_binop = 1;
+	for (i = 0; i < v->len; i++)
+	{
+		if (!is_binop_char(v->ptr[i]))
+		{
+			is_binop = 0;
+			break;
+		}
+	}
+
+	return is_binop? HAK_TOK_BINOP: HAK_TOK_SYMLIT;
 }
 
 static int is_sr_name_in_use (hak_t* hak, const hak_ooch_t* sr_name)
@@ -692,7 +753,7 @@ static HAK_INLINE hak_cnode_t* leave_list (hak_t* hak, hak_loc_t* list_loc, int*
 					/* check in advance if the array members are all plain symbols */
 					hak_cnode_t* lcar;
 					lcar = HAK_CNODE_CONS_CAR(tmp);
-					if (!HAK_CNODE_IS_SYMBOL_IDENT(lcar) && !HAK_CNODE_IS_DSYMBOL_CLA(lcar))
+					if (!HAK_CNODE_IS_SYMBOL(lcar) && !HAK_CNODE_IS_DSYMBOL_CLA(lcar))
 					{
 						hak_setsynerrbfmt(hak, HAK_SYNERR_LVALUE, HAK_CNODE_GET_LOC(lval), HAK_CNODE_GET_TOK(lval), "bad lvalue - invalid element in tuple");
 						goto oops;
@@ -718,7 +779,7 @@ static HAK_INLINE hak_cnode_t* leave_list (hak_t* hak, hak_loc_t* list_loc, int*
 			}
 			else
 			{
-				if (!HAK_CNODE_IS_SYMBOL_IDENT(lval) && !HAK_CNODE_IS_DSYMBOL_CLA(lval))
+				if (!HAK_CNODE_IS_SYMBOL(lval) && !HAK_CNODE_IS_DSYMBOL_CLA(lval))
 				{
 					hak_setsynerrbfmt(hak, HAK_SYNERR_LVALUE, HAK_CNODE_GET_LOC(lval), HAK_CNODE_GET_TOK(lval), "bad lvalue - invalid element");
 					goto oops;
@@ -1457,7 +1518,9 @@ static hak_cnode_type_t kw_to_cnode_type (int tok_type)
 		HAK_CNODE_REVERT,
 		HAK_CNODE_AND,
 		HAK_CNODE_OR,
+#if defined(USE_KW_PLUS)
 		HAK_CNODE_PLUS,
+#endif
 		HAK_CNODE_SET,
 		HAK_CNODE_SET_R
 	};
@@ -1477,22 +1540,68 @@ static int feed_process_token (hak_t* hak)
 	 * by manipulating its own stack. */
 
 /*hak_logbfmt(hak, HAK_LOG_STDERR, "TOKEN [%d] EOL[%d]=> [%.*js] type=%d LOC=%d.%d\n", TOKEN_TYPE(hak), HAK_TOK_EOL, TOKEN_NAME_LEN(hak), TOKEN_NAME_PTR(hak), TOKEN_TYPE(hak), TOKEN_LOC(hak)->line, TOKEN_LOC(hak)->colm);*/
+	if (frd->expect_pragma_item)
+	{
+		/* the pragmas changes the behavior of the reader and the compiler */
+		if (frd->expect_pragma_item >= 3) /* eol expected */
+		{
+			if (TOKEN_TYPE(hak) != HAK_TOK_EOL)
+			{
+				hak_setsynerrbfmt(hak, HAK_SYNERR_ILTOK, TOKEN_LOC(hak), HAK_NULL,
+					"redundant token '%.*js' for '%.*js'",
+					TOKEN_NAME_LEN(hak), TOKEN_NAME_PTR(hak),
+					vocas[VOCA_PRAGMA].len, vocas[VOCA_PRAGMA].str);
+				goto oops;
+			}
+			frd->expect_pragma_item = 0;
+		}
+		else
+		{
+			if (TOKEN_TYPE(hak) == HAK_TOK_EOL)
+			{
+				hak_setsynerrbfmt(hak, HAK_SYNERR_IDENT, TOKEN_LOC(hak), HAK_NULL,
+					"'%.*js' %hs not specified",
+					vocas[VOCA_PRAGMA].len, vocas[VOCA_PRAGMA].str,
+					(frd->expect_pragma_item == 1? "name": "value"));
+				goto oops;
+			}
+			else if (TOKEN_TYPE(hak) != HAK_TOK_IDENT)
+			{
+				hak_setsynerrbfmt(hak, HAK_SYNERR_IDENT, TOKEN_LOC(hak), HAK_NULL,
+					"'%.*js' %hs expected in place of '%.*js'",
+					vocas[VOCA_INCLUDE].len, vocas[VOCA_INCLUDE].str,
+					(frd->expect_pragma_item == 1? "name": "value"),
+					TOKEN_NAME_LEN(hak), TOKEN_NAME_PTR(hak));
+				goto oops;
+			}
+
+			if (frd->expect_pragma_item == 1)
+			{
+				frd->expect_pragma_item = 2; /* expect value */
+			}
+			else
+			{
+				frd->expect_pragma_item = 3; /* expect eol */
+			}
+		}
+		goto ok;
+	}
+
 	if (frd->expect_include_file)
 	{
 		/* the #include directive is an exception to the general expression rule.
 		 * use this exceptional code block to divert the major token processing */
-
 		if (TOKEN_TYPE(hak) == HAK_TOK_EOL)
 		{
 			hak_setsynerrbfmt(hak, HAK_SYNERR_STRING, TOKEN_LOC(hak), HAK_NULL,
-				"%.*js target not specified",
+				"'%.*js' target not specified",
 				vocas[VOCA_INCLUDE].len, vocas[VOCA_INCLUDE].str);
 			goto oops;
 		}
 		else if (TOKEN_TYPE(hak) != HAK_TOK_STRLIT)
 		{
 			hak_setsynerrbfmt(hak, HAK_SYNERR_STRING, TOKEN_LOC(hak), HAK_NULL,
-				"%.*js target expected in place of '%.*js'",
+				"'%.*js' target expected in place of '%.*js'",
 				vocas[VOCA_INCLUDE].len, vocas[VOCA_INCLUDE].str,
 				TOKEN_NAME_LEN(hak), TOKEN_NAME_PTR(hak));
 			goto oops;
@@ -1542,9 +1651,11 @@ static int feed_process_token (hak_t* hak)
 			goto ok;
 
 		case HAK_TOK_PRAGMA:
-			/* TODO: implement this */
-			hak_setsynerr(hak, HAK_SYNERR_ILTOK, TOKEN_LOC(hak), TOKEN_NAME(hak));
-			goto oops;
+			/*hak_setsynerr(hak, HAK_SYNERR_ILTOK, TOKEN_LOC(hak), TOKEN_NAME(hak));
+			goto oops;*/
+/* TODO: check if pragma is the first word in the line */
+			frd->expect_pragma_item = 1;
+			goto ok;
 
 		case HAK_TOK_VBAR:
 			if (frd->expect_vlist_item)
@@ -1729,15 +1840,14 @@ static int feed_process_token (hak_t* hak)
 				goto oops;
 			}
 			else if (can <= -1) goto oops;
-			if (can == 1) goto ident; /* if binop is the first in the list */
 
-			HAK_ASSERT(hak, can == 2);
-
-		#if 0
-/* TODO: ... */
+		#if 1
+			HAK_ASSERT(hak, can == 1 || can == 2);
 			frd->obj = hak_makecnodebinop(hak, 0, TOKEN_LOC(hak), TOKEN_NAME(hak));
-			goto ok;
+			goto auto_xlist;
 		#else
+			if (can == 1) goto ident; /* if binop is the first in the list */
+			HAK_ASSERT(hak, can == 2);
 			goto ident;
 		#endif
 		}
@@ -1897,7 +2007,9 @@ static int feed_process_token (hak_t* hak)
 		case HAK_TOK_REVERT:
 		case HAK_TOK_AND:
 		case HAK_TOK_OR:
+#if defined(USE_KW_PLUS)
 		case HAK_TOK_PLUS:
+#endif
 		case HAK_TOK_SET:
 		case HAK_TOK_SET_R:
 			frd->obj = hak_makecnode(hak, kw_to_cnode_type(TOKEN_TYPE(hak)), 0, TOKEN_LOC(hak), TOKEN_NAME(hak));
@@ -2360,7 +2472,7 @@ static int flx_start (hak_t* hak, hak_ooci_t c)
 		*/
 
 		case '$':
-			init_flx_di (FLX_DI(hak));
+			init_flx_di(FLX_DI(hak));
 			FEED_CONTINUE_WITH_CHAR(hak, c, HAK_FLX_DOLLARED_IDENT);
 			goto consumed;
 
@@ -2370,35 +2482,35 @@ static int flx_start (hak_t* hak, hak_ooci_t c)
 			goto consumed;
 
 		case '\"':
-			init_flx_qt (FLX_QT(hak), HAK_TOK_STRLIT, HAK_SYNERR_STRLIT, c, '\\', 0, HAK_TYPE_MAX(hak_oow_t), 0);
+			init_flx_qt(FLX_QT(hak), HAK_TOK_STRLIT, HAK_SYNERR_STRLIT, c, '\\', 0, HAK_TYPE_MAX(hak_oow_t), 0);
 			FEED_CONTINUE(hak, HAK_FLX_QUOTED_TOKEN); /* discard the quote itself. move on the the QUOTED_TOKEN state */
 			goto consumed;
 
 		case '\'':
-			init_flx_qt (FLX_QT(hak), HAK_TOK_CHARLIT, HAK_SYNERR_CHARLIT, c, '\\', 1, 1, 0);
+			init_flx_qt(FLX_QT(hak), HAK_TOK_CHARLIT, HAK_SYNERR_CHARLIT, c, '\\', 1, 1, 0);
 			FEED_CONTINUE(hak, HAK_FLX_QUOTED_TOKEN); /* discard the quote itself. move on the the QUOTED_TOKEN state */
 			goto consumed;
 
 #if defined(HAK_OOCH_IS_UCH) && defined(HAK_LANG_ENABLE_WIDE_DELIM)
 		case L'\u201C': /* “ ” */
-			init_flx_qt (FLX_QT(hak), HAK_TOK_STRLIT, HAK_SYNERR_STRLIT, L'\u201D', '\\', 0, HAK_TYPE_MAX(hak_oow_t), 0);
+			init_flx_qt(FLX_QT(hak), HAK_TOK_STRLIT, HAK_SYNERR_STRLIT, L'\u201D', '\\', 0, HAK_TYPE_MAX(hak_oow_t), 0);
 			FEED_CONTINUE(hak, HAK_FLX_QUOTED_TOKEN); /* discard the quote itself. move on the the QUOTED_TOKEN state */
 			goto consumed;
 		case L'\u2018': /* ‘ ’ */
-			init_flx_qt (FLX_QT(hak), HAK_TOK_CHARLIT, HAK_SYNERR_CHARLIT, L'\u2019', '\\', 1, 1, 0);
+			init_flx_qt(FLX_QT(hak), HAK_TOK_CHARLIT, HAK_SYNERR_CHARLIT, L'\u2019', '\\', 1, 1, 0);
 			FEED_CONTINUE(hak, HAK_FLX_QUOTED_TOKEN); /* discard the quote itself. move on the the QUOTED_TOKEN state */
 			goto consumed;
 #endif
 
 		case '+':
 		case '-':
-			init_flx_st (FLX_ST(hak), c);
+			init_flx_st(FLX_ST(hak), c);
 			FEED_CONTINUE_WITH_CHAR(hak, c, HAK_FLX_SIGNED_TOKEN);
 			goto consumed;
 
 		case '0': case '1': case '2': case '3': case '4':
 		case '5': case '6': case '7': case '8': case '9':
-			init_flx_pn (FLX_PN(hak), c);
+			init_flx_pn(FLX_PN(hak), c);
 			FEED_CONTINUE(hak, HAK_FLX_PLAIN_NUMBER);
 			goto not_consumed;
 
@@ -2411,14 +2523,17 @@ static int flx_start (hak_t* hak, hak_ooci_t c)
 			goto consumed;
 
 		default:
+#if defined(STRICT_BINOP)
 			if (is_binop_char(c))
 			{
-				init_flx_binop (FLX_BINOP(hak));
+				init_flx_binop(FLX_BINOP(hak));
 				FEED_CONTINUE(hak, HAK_FLX_BINOP);
 			}
-			else if (is_lead_ident_char(c))
+			else
+#endif
+			if (is_lead_ident_char(c))
 			{
-				init_flx_pi (FLX_PI(hak));
+				init_flx_pi(FLX_PI(hak));
 				FEED_CONTINUE(hak, HAK_FLX_PLAIN_IDENT);
 			}
 			else
@@ -2528,6 +2643,7 @@ static int flx_dollared_ident (hak_t* hak, hak_ooci_t c)
 		{
 			if (!is_lead_ident_char(c))
 			{
+				/* some character can't placed immediately after '$'. e.g '?' */
 				hak_setsynerrbfmt(hak, HAK_SYNERR_ILTOK, TOKEN_LOC(hak), HAK_NULL,
 					"'%c' prohibited as first character after '%.*js'",
 					c, TOKEN_NAME_LEN(hak), TOKEN_NAME_PTR(hak));
@@ -2586,12 +2702,14 @@ static int flx_hmarked_token (hak_t* hak, hak_ooci_t c)
 	 * #"..."   symbol literal
 	 */
 
+#if defined(STRICT_BINOP)
 	if (is_binop_char(c))
 	{
 		reset_flx_token(hak);
 		FEED_CONTINUE_WITH_CHAR(hak, c, HAK_FLX_HMARKED_BINOP);
 		goto consumed;
 	}
+#endif
 
 	switch (c)
 	{
@@ -2607,11 +2725,11 @@ static int flx_hmarked_token (hak_t* hak, hak_ooci_t c)
 
 	#if 0
 		case 'x': /* hexadecimal number */
-			init_flx_hn (FLX_HN(hak), HAK_TOK_RADNUMLIT, HAK_SYNERR_NUMLIT, 16);
+			init_flx_hn(FLX_HN(hak), HAK_TOK_RADNUMLIT, HAK_SYNERR_NUMLIT, 16);
 			goto radixed_number;
 
 		case 'o': /* octal number */
-			init_flx_hn (FLX_HN(hak), HAK_TOK_RADNUMLIT, HAK_SYNERR_NUMLIT, 8);
+			init_flx_hn(FLX_HN(hak), HAK_TOK_RADNUMLIT, HAK_SYNERR_NUMLIT, 8);
 			goto radixed_number;
 	#endif
 
@@ -2889,6 +3007,7 @@ static int flx_plain_ident (hak_t* hak, hak_ooci_t c) /* identifier */
 		start = TOKEN_NAME_LEN(hak) - pi->seg_len;
 		seg.ptr = &TOKEN_NAME_CHAR(hak, start);
 		seg.len = pi->seg_len;
+#if defined(STRICT_BINOP)
 		if (seg.ptr[seg.len - 1] == '-')
 		{
 			hak_setsynerrbfmt(hak, HAK_SYNERR_ILTOK, TOKEN_LOC(hak), TOKEN_NAME(hak),
@@ -2896,6 +3015,7 @@ static int flx_plain_ident (hak_t* hak, hak_ooci_t c) /* identifier */
 				seg.ptr[seg.len - 1]);
 			return -1;
 		}
+#endif
 		tok_type = classify_ident_token(hak, &seg);
 		if (tok_type != HAK_TOK_IDENT)
 		{
@@ -3328,7 +3448,16 @@ static int flx_signed_token (hak_t* hak, hak_ooci_t c)
 	}
 	else
 	{
-	#if 0
+	#if defined(STRICT_BINOP)
+		/* the leading sign must be + or - and must be one of the binop chars. */
+		HAK_ASSERT(hak, is_binop_char(st->sign_c));/* must be + or - and they must be one of the binop chars. */
+
+		/* switch to binop mode */
+		init_flx_binop(FLX_BINOP(hak));
+		HAK_ASSERT(hak, TOKEN_NAME_LEN(hak) == 1);
+		FEED_CONTINUE(hak, HAK_FLX_BINOP);
+		goto not_consumed;
+	#else
 		init_flx_pi(FLX_PI(hak));
 
 		/* the sign is already in the token name buffer.
@@ -3340,15 +3469,6 @@ static int flx_signed_token (hak_t* hak, hak_ooci_t c)
 		/* let refeeding of 'c' happen at the next iteration */
 		FEED_CONTINUE(hak, HAK_FLX_PLAIN_IDENT);
 		goto not_consumed;
-	#else
-		/* the leading sign must be + or - and must be one of the binop chars. */
-		HAK_ASSERT(hak, is_binop_char(st->sign_c));/* must be + or - and they must be one of the binop chars. */
-
-		/* switch to binop mode */
-		init_flx_binop(FLX_BINOP(hak));
-		HAK_ASSERT(hak, TOKEN_NAME_LEN(hak) == 1);
-		FEED_CONTINUE(hak, HAK_FLX_BINOP);
-		goto not_consumed;
 	#endif
 	}
 
diff --git a/src/kernel.hak b/src/kernel.hak
index cf7368e..84405fc 100644
--- a/src/kernel.hak
+++ b/src/kernel.hak
@@ -6,12 +6,12 @@ class Apex {
 		return (core.basicNew self size)
 	}
 
-	fun[#class] respondsTo(mth) {
-		return (core.classRespondsTo self mth)
+	fun[#class] respondsTo(mthname) {
+		return (core.classRespondsTo self mthname)
 	}
 
-	fun respondsTo(mth) {
-		return (core.instRespondsTo self mth)
+	fun respondsTo(mthname) {
+		return (core.instRespondsTo self mthname)
 	}
 
 	fun primAt(pos) {
diff --git a/t/call-5001.err b/t/call-5001.err
index 6b4cc0b..df56eef 100644
--- a/t/call-5001.err
+++ b/t/call-5001.err
@@ -105,3 +105,33 @@ core.basicAtPut "xbcdefghiklmnl" 4 k ##ERROR: exception not handled - "receiver
 
 k := (core.basicAt #abcdefg 1)
 core.basicAtPut #xbcdefghiklmnl 4 k ##ERROR: exception not handled - "receiver immutable - xbcdefghiklmnl"
+
+---
+
+## the compiler/runtime needs to improve on this although this is an error for now.
+fun + (a b) {}
+printf "%O\n" #{+: 20} ##ERROR: no builtin hash implemented for #<BLOCK>
+
+---
+
+class X {
+	fun + () {} ##ERROR: syntax error - only one argument expected for '+'
+}
+
+---
+
+## the binop method defined for a class must have one argument
+class X {
+	fun + (t) {}
+	fun f1 (t1 t2) {}
+}
+
+fun X:- (a b) {} ##ERROR: syntax error - only one argument expected for 'X:-'
+
+---
+
+class X {
+     fun[#ci] +(a b c) { printf "jjj\n" } ## the one argument rule applies to binary instance methods only.
+     fun +(c d) { printf "jjj\n" } ##ERROR: syntax error - only one argument expected for '+'
+}
+
diff --git a/t/feed-01.hak b/t/feed-01.hak
index ddf6cd9..9ed9bb0 100644
--- a/t/feed-01.hak
+++ b/t/feed-01.hak
@@ -132,6 +132,7 @@ if (== i k) { printf "OK: i is %d\n" i k } \
 else { printf "ERROR: i is not equal to %d\n" k }
 
 
+## dictionary
 a := #{
   (if (> 10 20) true else false ): 10,
   (if (< 10 20) true else false ): 20
diff --git a/t/feed-5001.err b/t/feed-5001.err
index cf68713..f70f9de 100644
--- a/t/feed-5001.err
+++ b/t/feed-5001.err
@@ -166,6 +166,7 @@ abc.? := 20 ##ERROR: syntax error - '?' prohibited as first character of identif
 
 
 ---
+
 - := 20 ##ERROR: syntax error - bad lvalue - invalid element - -
 
 ---
diff --git a/t/fun-01.hak b/t/fun-01.hak
index 0a16686..73004ff 100644
--- a/t/fun-01.hak
+++ b/t/fun-01.hak
@@ -126,3 +126,22 @@ if (== v 30) { printf "OK - %d\n" v } else { printf "ERROR - %d, not 30\n" v };
 fun k(x) (+ x 30)  ## (+ x 30) is valid function body
 v := (k 10)
 if (== v 40) { printf "OK - %d\n" v } else { printf "ERROR - %d, not 40\n" v };
+
+
+## ----------------------------------------
+fun plus(x y) {
+     ##printf "plus %d %d\n" x y
+     fun minus(x y) {
+          ##printf "minus %d %d\n" x y
+          - x y
+     }
+     + x y
+}
+
+fun dummy(q) {
+     printf "%s\n" q
+}
+
+plus 10 20 ## minus is now available after plus is executed
+v := (minus 10 1)
+if (== v 9) { printf "OK - %d\n" v } else { printf "ERROR - %d, not 9\n" v }