diff --git a/qse/cmd/awk/awk.c b/qse/cmd/awk/awk.c
index 63eca514..1c8055f2 100644
--- a/qse/cmd/awk/awk.c
+++ b/qse/cmd/awk/awk.c
@@ -1,5 +1,5 @@
 /*
- * $Id: awk.c 220 2009-07-01 13:14:39Z hyunghwan.chung $
+ * $Id: awk.c 236 2009-07-16 08:27:53Z hyunghwan.chung $
  *
    Copyright 2006-2009 Chung, Hyung-Hwan.
 
@@ -233,14 +233,7 @@ static int apply_fs_and_gvm (qse_awk_rtx_t* rtx, struct arg_t* arg)
 	return 0;
 }
 
-static int on_loop_enter (qse_awk_rtx_t* rtx, void* data)
-{
-	/* TODO: anything to do? */
-	return 0;
-}
-
-static void on_loop_exit (
-	qse_awk_rtx_t* rtx, qse_awk_val_t* ret, void* data)
+static void dprint_return (qse_awk_rtx_t* rtx, qse_awk_val_t* ret)
 {
 	qse_size_t len;
 	qse_char_t* str;
@@ -274,8 +267,7 @@ static void on_statement (
 	/*dprint (L"running %d\n", (int)line);*/
 }
 
-static int fnc_sleep (
-	qse_awk_rtx_t* run, const qse_char_t* fnm, qse_size_t fnl)
+static int fnc_sleep (qse_awk_rtx_t* run, const qse_cstr_t* fnm)
 {
 	qse_size_t nargs;
 	qse_awk_val_t* a0;
@@ -681,6 +673,7 @@ static int awk_main (int argc, qse_char_t* argv[])
 {
 	qse_awk_t* awk = QSE_NULL;
 	qse_awk_rtx_t* rtx = QSE_NULL;
+	qse_awk_val_t* retv;
 	qse_awk_rcb_t rcb;
 
 	int i;
@@ -751,8 +744,6 @@ static int awk_main (int argc, qse_char_t* argv[])
 		goto oops;
 	}
 
-	rcb.on_loop_enter = on_loop_enter;
-	rcb.on_loop_exit = on_loop_exit;
 	rcb.on_statement = on_statement;
 	rcb.udd = &arg;
 
@@ -773,18 +764,18 @@ static int awk_main (int argc, qse_char_t* argv[])
 	qse_awk_rtx_setrcb (rtx, &rcb);
 
 	set_intr_run ();
-	if (arg.call == QSE_NULL)
+
+	retv = (arg.call == QSE_NULL)?
+		qse_awk_rtx_loop (rtx):
+		qse_awk_rtx_call (rtx, arg.call, QSE_NULL, 0);
+	if (retv != QSE_NULL)
 	{
-		ret = qse_awk_rtx_loop (rtx);
-	}
-	else
-	{
-		qse_awk_val_t* rv;
-		
-		rv = qse_awk_rtx_call (rtx, arg.call, QSE_NULL, 0);
-		ret = (rv == QSE_NULL)? -1: 0;
-		qse_awk_rtx_refdownval (rtx, rv);
+		qse_awk_rtx_refdownval (rtx, retv);
+		ret = 0;
+
+		dprint_return (rtx, retv);
 	}
+
 	unset_intr_run ();
 
 	if (ret <= -1)
diff --git a/qse/include/qse/awk/Awk.hpp b/qse/include/qse/awk/Awk.hpp
index 7e3a1aac..e6174bd1 100644
--- a/qse/include/qse/awk/Awk.hpp
+++ b/qse/include/qse/awk/Awk.hpp
@@ -1,5 +1,5 @@
 /*
- * $Id: Awk.hpp 235 2009-07-15 10:43:31Z hyunghwan.chung $
+ * $Id: Awk.hpp 236 2009-07-16 08:27:53Z hyunghwan.chung $
  *
    Copyright 2006-2009 Chung, Hyung-Hwan.
 
@@ -255,7 +255,9 @@ protected:
 	void retrieveError (Run* run);
 	/*@}*/
 
+protected:
 	class NoSource;
+
 public:
 	/** 
 	 * The Source class is an abstract class to encapsulate
@@ -677,6 +679,7 @@ public:
 		static const char_t* EMPTY_STRING;
 	};
 
+public:
 	/**
 	 * Defines an identifier of predefined global variables.
 	 * Awk::setGlobal and Awk::getGlobal can take one of these enumerators.
@@ -802,24 +805,26 @@ public:
 	 * @return a Run object on success, #QSE_NULL on failure
 	 */
 	Awk::Run* parse (
-		Source& in,  /**< script to parse */
-		Source& out  /**< deparsing target */
+		Source& in,  ///< script to parse 
+		Source& out  ///< deparsing target 
 	);
 
 	/**
 	 * Executes the BEGIN block, pattern-action blocks, and the END block.
 	 * @return 0 on succes, -1 on failure
 	 */
-	int loop ();
+	int loop (
+		Value* ret  ///< return value holder
+	);
 
 	/**
 	 * Calls a function
 	 */
 	int call (
-		const char_t* name,
-		Value*        ret,
-		const Value*  args,
-		size_t        nargs
+		const char_t* name,  ///< function name
+		Value*        ret,   ///< return value holder
+		const Value*  args,  ///< argument array
+		size_t        nargs  ///< number of arguments
 	);
 
 	/**
@@ -982,16 +987,6 @@ public:
 	int deleteFunction (const char_t* name);
 	/*@}*/
 
-	/**
-	 * Enables the run-time callback
-	 */
-	void enableRunCallback ();
-
-	/**
-	 * Disables the run-time callback
-	 */
-	void disableRunCallback ();
-
 	/**
 	 * @name Word Substitution
 	 */
@@ -1058,11 +1053,6 @@ protected:
 	virtual int     nextConsole  (Console& io) = 0;
 	/*@}*/
 
-	// run-time callbacks
-	virtual bool onLoopEnter (Run& run);
-	virtual void onLoopExit (Run& run, const Value& ret);
-	virtual void onStatement (Run& run, size_t line);
-	
 	// primitive handlers 
 	virtual real_t pow (real_t x, real_t y) = 0;
 	virtual int    vsprintf (char_t* buf, size_t size,
@@ -1086,10 +1076,6 @@ protected:
 
 	static int functionHandler (rtx_t* rtx, const cstr_t* name);
 
-	static int  onLoopEnter (rtx_t* run, void* data);
-	static void onLoopExit (rtx_t* run, val_t* ret, void* data);
-	static void onStatement (rtx_t* run, size_t line, void* data);
-
 	static real_t pow     (awk_t* data, real_t x, real_t y);
 	static int    sprintf (awk_t* data, char_t* buf, size_t size,
 	                       const char_t* fmt, ...);
@@ -1108,8 +1094,6 @@ protected:
 	Source* sourceReader;
 	Source* sourceWriter;
 
-	bool     runCallback;
-
 	struct xstrs_t
 	{
 		xstrs_t (): ptr (QSE_NULL), len (0), capa (0) {}
diff --git a/qse/include/qse/awk/awk.h b/qse/include/qse/awk/awk.h
index da6b5849..43c10c65 100644
--- a/qse/include/qse/awk/awk.h
+++ b/qse/include/qse/awk/awk.h
@@ -1,5 +1,5 @@
 /*
- * $Id: awk.h 235 2009-07-15 10:43:31Z hyunghwan.chung $
+ * $Id: awk.h 236 2009-07-16 08:27:53Z hyunghwan.chung $
  *
    Copyright 2006-2009 Chung, Hyung-Hwan.
 
@@ -58,7 +58,9 @@
  * awk = qse_awk_open (mmgr, 0, prm); // create an interpreter 
  * qse_awk_parse (awk, &sio);          // parse a script 
  * rtx = qse_awk_rtx_open (awk, 0, &rio, args); // create a runtime context 
- * qse_awk_rtx_loop (rtx);            // run a standard AWK loop 
+ * retv = qse_awk_rtx_loop (rtx);     // run a standard AWK loop 
+ * if (retv != QSE_NULL) 
+ *    qse_awk_rtx_refdownval (rtx, retv); // free return value
  * qse_awk_rtx_close (rtx);           // destroy the runtime context
  * qse_awk_close (awk);               // destroy the interpreter
  * @endcode
@@ -466,20 +468,6 @@ typedef struct qse_awk_rio_t qse_awk_rio_t;
  */
 struct qse_awk_rcb_t
 {
-	/** 
-	 * called by qse_awk_rtx_loop() before entering pattern-action loop.
-	 * A @b BEGIN block is executed after this callback.
-	 */
-	int (*on_loop_enter) (
-		qse_awk_rtx_t* rtx, void* udd);
-
-	/**
-	 * called by qse_awk_rtx_loop() when exiting pattern-action loop.
-	 * An @b END block is executed before this callback.
-	 */
-	void (*on_loop_exit) (
-		qse_awk_rtx_t* rtx, qse_awk_val_t* ret, void* udd);
-
 	/**
 	 * called by qse_awk_rtx_loop() and qse_awk_rtx_call() for
 	 * each statement executed.
@@ -1304,22 +1292,25 @@ void qse_awk_rtx_close (
 
 /**
  * The qse_awk_rtx_loop() function executes the BEGIN block, pattern-action
- * blocks and the END blocks in an AWk program. Multiple invocations of the
- * function for the lifetime of a runtime context is not desirable.
+ * blocks and the END blocks in an AWk program. It returns the global return 
+ * value of which the reference count must be decremented when not necessary. 
+ * Multiple invocations of the function for the lifetime of a runtime context 
+ * is not desirable.
  *
+ * The example shows typical usage of the function.
  * @code
- *  The example shows typical usage of the function.
- *    rtx = qse_awk_rtx_open (awk, 0, rio, QSE_NULL);
- *    if (rtx != QSE_NULL)
- *    {
- *        qse_awk_rtx_loop (rtx);
- *        qse_awk_rtx_close (rtx);
- *    }
+ * rtx = qse_awk_rtx_open (awk, 0, rio, QSE_NULL);
+ * if (rtx != QSE_NULL)
+ * {
+ *    retv = qse_awk_rtx_loop (rtx);
+ *    if (retv != QSE_NULL) qse_awk_rtx_refdownval (rtx, retv);
+ *    qse_awk_rtx_close (rtx);
+ * }
  * @endcode
  *
- * @return 0 on success, -1 on failure.
+ * @return return value on success, QSE_NULL on failure.
  */
-int qse_awk_rtx_loop (
+qse_awk_val_t* qse_awk_rtx_loop (
 	qse_awk_rtx_t* rtx /**< runtime context */
 );
 
diff --git a/qse/include/qse/cmn/rex.h b/qse/include/qse/cmn/rex.h
index e75e87ad..24590290 100644
--- a/qse/include/qse/cmn/rex.h
+++ b/qse/include/qse/cmn/rex.h
@@ -1,5 +1,5 @@
 /*
- * $Id: rex.h 203 2009-06-17 12:43:50Z hyunghwan.chung $
+ * $Id: rex.h 236 2009-07-16 08:27:53Z hyunghwan.chung $
  *
    Copyright 2006-2009 Chung, Hyung-Hwan.
 
@@ -54,6 +54,7 @@
  *
  * @todo
  * - support \\n to refer to the nth matching substring
+ * - change to adopt Thomson's NFA (http://swtch.com/~rsc/regexp/regexp1.html)
  */
 
 #define QSE_REX_NA(code) (*(qse_size_t*)(code))
diff --git a/qse/lib/awk/Awk.cpp b/qse/lib/awk/Awk.cpp
index e1577668..2294e5e2 100644
--- a/qse/lib/awk/Awk.cpp
+++ b/qse/lib/awk/Awk.cpp
@@ -1,5 +1,5 @@
 /*
- * $Id: Awk.cpp 235 2009-07-15 10:43:31Z hyunghwan.chung $
+ * $Id: Awk.cpp 236 2009-07-16 08:27:53Z hyunghwan.chung $
  *
    Copyright 2006-2009 Chung, Hyung-Hwan.
 
@@ -21,6 +21,9 @@
 #include "../cmn/mem.h"
 #include "awk.h"
 
+// enable this once addFunction() is extended with argument spec (rxv...).
+//#define PASS_BY_REFERENCE
+
 /////////////////////////////////
 QSE_BEGIN_NAMESPACE(QSE)
 /////////////////////////////////
@@ -994,7 +997,7 @@ int Awk::Run::getGlobal (int id, Value& g) const
 
 Awk::Awk () : awk (QSE_NULL), functionMap (QSE_NULL),
 	sourceIn (this, Source::READ), sourceOut (this, Source::WRITE),
-	runCallback (false), runctx (this)
+	runctx (this)
 
 {
 	errinf.num = (errnum_t)ERR_NOERR;
@@ -1140,7 +1143,6 @@ int Awk::open ()
 	qse_map_setfreeer (functionMap, QSE_MAP_VAL, free_function_map_value);
 	qse_map_setscale (functionMap, QSE_MAP_KEY, QSE_SIZEOF(qse_char_t));
 
-	runCallback = false;
 	return 0;
 }
 
@@ -1162,7 +1164,6 @@ void Awk::close ()
 	}
 
 	clearError ();
-	runCallback = false;
 }
 
 Awk::Run* Awk::parse (Source& in, Source& out) 
@@ -1195,19 +1196,27 @@ Awk::Run* Awk::parse (Source& in, Source& out)
 	return &runctx;
 }
 
-int Awk::loop () 
+int Awk::loop (Value* ret)
 {
 	QSE_ASSERT (awk != QSE_NULL);
 	QSE_ASSERT (runctx.rtx != QSE_NULL);
 
-	int n = qse_awk_rtx_loop (runctx.rtx);
-	if (n <= -1) retrieveError (&runctx);
-	return n;
+	val_t* rv = qse_awk_rtx_loop (runctx.rtx);
+	if (rv == QSE_NULL) 
+	{
+		retrieveError (&runctx);
+		return -1;
+	}
+
+	ret->setVal (&runctx, rv);
+	qse_awk_rtx_refdownval (runctx.rtx, rv);
+	
+	return 0;
 }
 
 int Awk::call (
 	const char_t* name, Value* ret,
-	const Value* args, size_t nargs) 
+	const Value* args, size_t nargs)
 {
 	QSE_ASSERT (awk != QSE_NULL);
 	QSE_ASSERT (runctx.rtx != QSE_NULL);
@@ -1260,21 +1269,11 @@ int Awk::init_runctx ()
 	if (runctx.rtx != QSE_NULL) return 0;
 
 	qse_awk_rio_t rio;
-	qse_awk_rcb_t rcb;
 
 	rio.pipe    = pipeHandler;
 	rio.file    = fileHandler;
 	rio.console = consoleHandler;
 
-	if (runCallback)
-	{
-		QSE_MEMSET (&rcb, 0, QSE_SIZEOF(rcb));
-		rcb.on_loop_enter = onLoopEnter;
-		rcb.on_loop_exit  = onLoopExit;
-		rcb.on_statement  = onStatement;
-		rcb.udd           = &runctx;
-	}
-
 	rtx_t* rtx = qse_awk_rtx_open (
 		awk, QSE_SIZEOF(rxtn_t), &rio, (qse_cstr_t*)runarg.ptr);
 	if (rtx == QSE_NULL) 
@@ -1288,7 +1287,6 @@ int Awk::init_runctx ()
 	rxtn_t* rxtn = (rxtn_t*) QSE_XTN (rtx);
 	rxtn->run = &runctx;
 
-	if (runCallback) qse_awk_rtx_setrcb (rtx, &rcb);
 	return 0;
 }
 
@@ -1357,12 +1355,23 @@ int Awk::dispatch_function (Run* run, const cstr_t* name)
 	for (i = 0; i < nargs; i++)
 	{
 		val_t* v = qse_awk_rtx_getarg (run->rtx, i);
+#ifdef PASS_BY_REFERENCE
+		QSE_ASSERT (v->type == QSE_AWK_VAL_REF);
+		val_t** ref = (val_t**)((qse_awk_val_ref_t*)v)->adr;
+		if (args[i].setVal (run, *ref) == -1)
+		{
+			run->setError (ERR_NOMEM);
+			if (args != buf) delete[] args;
+			return -1;
+		}
+#else
 		if (args[i].setVal (run, v) == -1)
 		{
 			run->setError (ERR_NOMEM);
 			if (args != buf) delete[] args;
 			return -1;
 		}
+#endif
 	}
 	
 	Value ret (run);
@@ -1372,6 +1381,28 @@ int Awk::dispatch_function (Run* run, const cstr_t* name)
 	try { n = (this->*handler) (*run, ret, args, nargs, name); }
 	catch (...) { n = -1; }
 
+#ifdef PASS_BY_REFERENCE
+	if (n >= 0)
+	{
+		for (i = 0; i < nargs; i++)
+		{
+			QSE_ASSERTX (args[i].run == run, 
+				"Do NOT change Run from function handler");
+
+			val_t* v = qse_awk_rtx_getarg (run->rtx, i);
+			val_t* nv = args[i].toVal();
+
+			if (nv == v) continue;
+
+			QSE_ASSERT (v->type == QSE_AWK_VAL_REF);
+			val_t** ref = (val_t**)((qse_awk_val_ref_t*)v)->adr;
+	
+			qse_awk_rtx_refdownval (run->rtx, *ref);
+			*ref = nv;
+			qse_awk_rtx_refupval (run->rtx, *ref);
+		}
+	}
+#endif
 	if (args != buf) delete[] args;
 
 	if (n <= -1) 
@@ -1505,9 +1536,15 @@ int Awk::addFunction (
 	
 	size_t nameLen = qse_strlen(name);
 
-	void* p = qse_awk_addfnc (awk, name, nameLen,
-	                          0, minArgs, maxArgs, QSE_NULL, 
-	                          functionHandler);
+	void* p = qse_awk_addfnc (
+		awk, name, nameLen,
+		0, minArgs, maxArgs,
+#ifdef PASS_BY_REFERENCE
+		QSE_T("R"), // pass all arguments by reference
+#else
+		QSE_NULL,
+#endif
+		functionHandler);
 	if (p == QSE_NULL) 
 	{
 		qse_awk_free (awk, tmp);
@@ -1542,16 +1579,6 @@ int Awk::deleteFunction (const char_t* name)
 	return n;
 }
 
-void Awk::enableRunCallback () 
-{
-	runCallback = true;
-}
-
-void Awk::disableRunCallback () 
-{
-	runCallback = false;
-}
-
 int Awk::getWord (
 	const char_t* ow, qse_size_t owl,
 	const char_t** nw, qse_size_t* nwl) 
@@ -1590,20 +1617,6 @@ int Awk::unsetAllWords ()
 	return qse_awk_setword (awk, QSE_NULL, 0, QSE_NULL, 0);
 }
 
-
-bool Awk::onLoopEnter (Run& run)
-{
-	return true;
-}
-
-void Awk::onLoopExit (Run& run, const Value& ret)
-{
-}
-
-void Awk::onStatement (Run& run, size_t line)
-{
-}
-
 Awk::ssize_t Awk::readSource (
 	awk_t* awk, qse_awk_sio_cmd_t cmd, char_t* data, size_t count)
 {
@@ -1762,28 +1775,6 @@ int Awk::functionHandler (rtx_t* rtx, const cstr_t* name)
 	return rxtn->run->awk->dispatch_function (rxtn->run, name);
 }	
 
-int Awk::onLoopEnter (rtx_t* rtx, void* data)
-{
-	Run* run = (Run*)data;
-	return run->awk->onLoopEnter(*run)? 0: -1;
-}
-
-void Awk::onLoopExit (rtx_t* rtx, val_t* ret, void* data)
-{
-	Run* run = (Run*)data;
-
-	Value x;
-	if (x.setVal (run, ret) == -1) 
-		qse_awk_rtx_seterrnum (run->rtx, (errnum_t)ERR_NOMEM);
-	else run->awk->onLoopExit (*run, x);
-}
-
-void Awk::onStatement (rtx_t* rtx, size_t line, void* data)
-{
-	Run* run = (Run*)data;
-	run->awk->onStatement (*run, line);
-}
-
 Awk::real_t Awk::pow (awk_t* awk, real_t x, real_t y)
 {
 	xtn_t* xtn = (xtn_t*) QSE_XTN (awk);
diff --git a/qse/lib/awk/run.c b/qse/lib/awk/run.c
index c4929608..389e2ebf 100644
--- a/qse/lib/awk/run.c
+++ b/qse/lib/awk/run.c
@@ -1,5 +1,5 @@
 /*
- * $Id: run.c 235 2009-07-15 10:43:31Z hyunghwan.chung $
+ * $Id: run.c 236 2009-07-16 08:27:53Z hyunghwan.chung $
  *
    Copyright 2006-2009 Chung, Hyung-Hwan.
 
@@ -1318,30 +1318,17 @@ static void exit_stack_frame (qse_awk_rtx_t* run)
 	run->stack_base = (qse_size_t)run->stack[run->stack_base+0];
 }
 
-static int run_bpae_loop (qse_awk_rtx_t* rtx)
+static qse_awk_val_t* run_bpae_loop (qse_awk_rtx_t* rtx)
 {
 	qse_awk_nde_t* nde;
 	qse_size_t nargs, i;
-	qse_awk_val_t* v;
+	qse_awk_val_t* retv;
 	int ret = 0;
 
 	/* set nargs to zero */
 	nargs = 0;
 	STACK_NARGS(rtx) = (void*)nargs;
 
-	/* call the callback */
-	if (rtx->rcb.on_loop_enter != QSE_NULL)
-	{
-		qse_awk_rtx_seterrnum (rtx, QSE_AWK_ENOERR);
-		ret = rtx->rcb.on_loop_enter (rtx, rtx->rcb.udd);
-		if (ret <= -1) 
-		{
-			if (rtx->errinf.num == QSE_AWK_ENOMEM)
-				qse_awk_rtx_seterrnum (rtx, QSE_AWK_EUNKNOWN);
-			ret = -1;
-		}
-	}
-
 	/* execute the BEGIN block */
 	for (nde = rtx->awk->tree.begin; 
 	     ret == 0 && nde != QSE_NULL && rtx->exit_level < EXIT_GLOBAL;
@@ -1357,7 +1344,7 @@ static int run_bpae_loop (qse_awk_rtx_t* rtx)
 		if (run_block (rtx, blk) == -1) ret = -1;
 	}
 
-	if (ret == -1 && rtx->errinf.num == QSE_AWK_ENOERR) 
+	if (ret <= -1 && rtx->errinf.num == QSE_AWK_ENOERR) 
 	{
 		/* an error is returned with no error number set.
 		 * this feature is used by eval_expression() to
@@ -1374,10 +1361,10 @@ static int run_bpae_loop (qse_awk_rtx_t* rtx)
 	     rtx->awk->tree.end != QSE_NULL) && 
 	     rtx->exit_level < EXIT_GLOBAL)
 	{
-		if (run_pattern_blocks(rtx) == -1) ret = -1;
+		if (run_pattern_blocks(rtx) <= -1) ret = -1;
 	}
 
-	if (ret == -1 && rtx->errinf.num == QSE_AWK_ENOERR)
+	if (ret <= -1 && rtx->errinf.num == QSE_AWK_ENOERR)
 	{
 		/* an error is returned with no error number set.
 		 * this feature is used by eval_expression() to
@@ -1401,7 +1388,7 @@ static int run_bpae_loop (qse_awk_rtx_t* rtx)
 
 		rtx->active_block = blk;
 		rtx->exit_level = EXIT_NONE;
-		if (run_block (rtx, blk) == -1) ret = -1;
+		if (run_block (rtx, blk) <= -1) ret = -1;
 		else if (rtx->exit_level >= EXIT_GLOBAL) 
 		{
 			/* once exit is called inside one of END blocks,
@@ -1410,7 +1397,7 @@ static int run_bpae_loop (qse_awk_rtx_t* rtx)
 		}
 	}
 
-	if (ret == -1 && rtx->errinf.num == QSE_AWK_ENOERR)
+	if (ret <= -1 && rtx->errinf.num == QSE_AWK_ENOERR)
 	{
 		/* an error is returned with no error number set.
 		 * this feature is used by eval_expression() to
@@ -1430,39 +1417,34 @@ static int run_bpae_loop (qse_awk_rtx_t* rtx)
 		qse_awk_rtx_refdownval (rtx, STACK_ARG(rtx,i));
 
 	/* get the return value in the current stack frame */
-	v = STACK_RETVAL(rtx);
+	retv = STACK_RETVAL(rtx);
 
-	if (rtx->rcb.on_loop_exit != QSE_NULL)
+	if (ret <= -1)
 	{
-		/* we call the on_exit handler regardless of ret. 
-		 * the return value passed is the global return value
-		 * in the stack. */
-		rtx->rcb.on_loop_exit (rtx, v, rtx->rcb.udd);
+		/* end the life of the global return value upon error */
+		qse_awk_rtx_refdownval (rtx, retv);
+		retv = QSE_NULL;
 	}
 
-	/* end the life of the global return value */
-	qse_awk_rtx_refdownval (rtx, v);
-
-	return ret;
+	return retv;
 }
 
 /* start the BEGIN-pattern block-END loop */
-int qse_awk_rtx_loop (qse_awk_rtx_t* rtx)
+qse_awk_val_t* qse_awk_rtx_loop (qse_awk_rtx_t* rtx)
 {
-	int ret;
+	qse_awk_val_t* retv = QSE_NULL;
 
 	rtx->exit_level = EXIT_NONE;
 
-	ret = enter_stack_frame (rtx);
-	if (ret == 0)
+	if (enter_stack_frame (rtx) == 0)
 	{
-		ret = run_bpae_loop (rtx);
+		retv = run_bpae_loop (rtx);
 		exit_stack_frame (rtx);
 	}
 
 	/* reset the exit level */
 	rtx->exit_level = EXIT_NONE;
-	return ret;
+	return retv;
 }
 
 /* call an AWK function */
@@ -5846,7 +5828,8 @@ static qse_size_t push_arg_from_nde (
 			 qse_strlen(fnc_arg_spec) > nargs));
 
 		if (fnc_arg_spec != QSE_NULL && 
-		    fnc_arg_spec[nargs] == QSE_T('r'))
+		    (fnc_arg_spec[nargs] == QSE_T('r') ||
+		     fnc_arg_spec[0] == QSE_T('R')))
 		{
 			qse_awk_val_t** ref;
 			      
@@ -5872,6 +5855,7 @@ static qse_size_t push_arg_from_nde (
 		{
 			v = eval_expression (rtx, p);
 		}
+
 		if (v == QSE_NULL)
 		{
 			UNWIND_RTX_STACK_ARG (rtx, nargs);
diff --git a/qse/lib/awk/tree.h b/qse/lib/awk/tree.h
index 0373aec7..c8aca547 100644
--- a/qse/lib/awk/tree.h
+++ b/qse/lib/awk/tree.h
@@ -1,5 +1,5 @@
 /*
- * $Id: tree.h 235 2009-07-15 10:43:31Z hyunghwan.chung $
+ * $Id: tree.h 236 2009-07-16 08:27:53Z hyunghwan.chung $
  *
    Copyright 2006-2009 Chung, Hyung-Hwan.
 
@@ -76,6 +76,8 @@ enum qse_awk_nde_type_t
 	QSE_AWK_NDE_GETLINE
 };
 
+typedef enum qse_awk_nde_type_t qse_awk_nde_type_t;
+
 enum qse_awk_in_type_t
 {
 	/* the order of these values match 
@@ -149,7 +151,7 @@ struct qse_awk_fun_t
 };
 
 #define QSE_AWK_NDE_HDR \
-	int type; \
+	qse_awk_nde_type_t type; \
 	qse_size_t line; \
 	qse_awk_nde_t* next
 
@@ -162,7 +164,7 @@ struct qse_awk_nde_t
 struct qse_awk_nde_blk_t
 {
 	QSE_AWK_NDE_HDR;
-	qse_size_t nlcls;
+	qse_size_t nlcls; /* number of local variables */
 	qse_awk_nde_t* body;
 };
 
diff --git a/qse/samples/awk/awk01.c b/qse/samples/awk/awk01.c
index 4254f0b8..a0b9cfcc 100644
--- a/qse/samples/awk/awk01.c
+++ b/qse/samples/awk/awk01.c
@@ -1,5 +1,5 @@
 /*
- * $Id: awk01.c 195 2009-06-10 13:18:25Z hyunghwan.chung $ 
+ * $Id: awk01.c 236 2009-07-16 08:27:53Z hyunghwan.chung $ 
  *
    Copyright 2006-2009 Chung, Hyung-Hwan.
 
@@ -35,13 +35,14 @@ int main ()
 {
 	qse_awk_t* awk = QSE_NULL;
 	qse_awk_rtx_t* rtx = QSE_NULL;
+	qse_awk_val_t* retv;
 	qse_awk_parsestd_in_t psin;
 	int ret;
 
 	awk = qse_awk_openstd (0);
 	if (awk == QSE_NULL)  
 	{
-		qse_fprintf (QSE_STDERR, QSE_T("error: cannot open awk\n"));
+		qse_fprintf (QSE_STDERR, QSE_T("ERROR: cannot open awk\n"));
 		goto oops;
 	}
 
@@ -49,11 +50,11 @@ int main ()
 	psin.u.cp  = src;
 
 	ret = qse_awk_parsestd (awk, &psin, QSE_NULL);
-	if (ret == -1)
+	if (ret <= -1)
 	{
-		qse_fprintf (QSE_STDERR, QSE_T("error: %s\n"), 
+		qse_fprintf (QSE_STDERR, QSE_T("ERROR: %s\n"), 
 			qse_awk_geterrmsg(awk));
-		goto oops;
+		ret = -1; goto oops;
 	}
 
 	rtx = qse_awk_rtx_openstd (
@@ -65,22 +66,25 @@ int main ()
 	);
 	if (rtx == QSE_NULL) 
 	{
-		qse_fprintf (QSE_STDERR, QSE_T("error: %s\n"), 
+		qse_fprintf (QSE_STDERR, QSE_T("ERROR: %s\n"), 
 			qse_awk_geterrmsg(awk));
-		goto oops;
+		ret = -1; goto oops;
 	}
 	
-	ret = qse_awk_rtx_loop (rtx);
-	if (ret == -1)
+	retv = qse_awk_rtx_loop (rtx);
+	if (retv == QSE_NULL)
 	{
-		qse_fprintf (QSE_STDERR, QSE_T("error: %s\n"), 
+		qse_fprintf (QSE_STDERR, QSE_T("ERROR: %s\n"), 
 			qse_awk_rtx_geterrmsg(rtx));
-		goto oops;
+		ret = -1; goto oops;
 	}
 
+	qse_awk_rtx_refdownval (rtx, retv);
+	ret = 0;
+
 oops:
 	if (rtx != QSE_NULL) qse_awk_rtx_close (rtx);
 	if (awk != QSE_NULL) qse_awk_close (awk);
-	return -1;
+	return ret;
 }
 
diff --git a/qse/samples/awk/awk02.c b/qse/samples/awk/awk02.c
index a068283a..a4434327 100644
--- a/qse/samples/awk/awk02.c
+++ b/qse/samples/awk/awk02.c
@@ -1,5 +1,5 @@
 /*
- * $Id: awk02.c 195 2009-06-10 13:18:25Z hyunghwan.chung $ 
+ * $Id: awk02.c 236 2009-07-16 08:27:53Z hyunghwan.chung $ 
  *
    Copyright 2006-2009 Chung, Hyung-Hwan.
 
@@ -38,6 +38,7 @@ int main ()
 {
 	qse_awk_t* awk = QSE_NULL;
 	qse_awk_rtx_t* rtx = QSE_NULL;
+	qse_awk_val_t* retv;
 
 	qse_awk_parsestd_in_t psin;
 	qse_awk_parsestd_out_t psout;
@@ -47,8 +48,8 @@ int main ()
 	awk = qse_awk_openstd (0);
 	if (awk == QSE_NULL)  
 	{
-		qse_fprintf (QSE_STDERR, QSE_T("error: cannot open awk\n"));
-		goto oops;
+		qse_fprintf (QSE_STDERR, QSE_T("ERROR: cannot open awk\n"));
+		ret = -1; goto oops;
 	}
 
 	qse_memset (srcout, QSE_T(' '), QSE_COUNTOF(srcout)-1);
@@ -60,11 +61,11 @@ int main ()
 	psout.u.cp  = srcout;
 
 	ret = qse_awk_parsestd (awk, &psin, &psout);
-	if (ret == -1)
+	if (ret <= -1)
 	{
-		qse_fprintf (QSE_STDERR, QSE_T("error: %s\n"), 
+		qse_fprintf (QSE_STDERR, QSE_T("ERROR: %s\n"), 
 			qse_awk_geterrmsg(awk));
-		goto oops;
+		ret = -1; goto oops;
 	}
 
 	qse_printf (QSE_T("DEPARSED SOURCE:\n%s\n"), srcout);
@@ -80,19 +81,22 @@ int main ()
 	);
 	if (rtx == QSE_NULL) 
 	{
-		qse_fprintf (QSE_STDERR, QSE_T("error: %s\n"), 
+		qse_fprintf (QSE_STDERR, QSE_T("ERROR: %s\n"), 
 			qse_awk_geterrmsg(awk));
-		goto oops;
+		ret = -1; goto oops;
 	}
 	
-	ret = qse_awk_rtx_loop (rtx);
-	if (ret == -1)
+	retv = qse_awk_rtx_loop (rtx);
+	if (retv == QSE_NULL)
 	{
-		qse_fprintf (QSE_STDERR, QSE_T("error: %s\n"), 
+		qse_fprintf (QSE_STDERR, QSE_T("ERROR: %s\n"), 
 			qse_awk_rtx_geterrmsg(rtx));
-		goto oops;
+		ret = -1; goto oops;
 	}
 
+	qse_awk_rtx_refdownval (rtx, retv);
+	ret = 0;
+
 oops:
 	if (rtx != QSE_NULL) qse_awk_rtx_close (rtx);
 	if (awk != QSE_NULL) qse_awk_close (awk);
diff --git a/qse/samples/awk/awk05.cpp b/qse/samples/awk/awk05.cpp
index 39e94ca1..b7d548ab 100644
--- a/qse/samples/awk/awk05.cpp
+++ b/qse/samples/awk/awk05.cpp
@@ -49,8 +49,9 @@ static int run_awk (QSE::StdAwk& awk)
 	// parse the script string and deparse it to awk05.out.
 	if (awk.parse (in, out) == QSE_NULL) return -1;
 
+	QSE::StdAwk::Value r;
 	// execute the BEGIN, pattern-action, END blocks.
-	return awk.loop ();
+	return awk.loop (&r);
 }
 
 static int awk_main (int argc, qse_char_t* argv[])
diff --git a/qse/samples/awk/awk06.cpp b/qse/samples/awk/awk06.cpp
index e165d693..fd4781ad 100644
--- a/qse/samples/awk/awk06.cpp
+++ b/qse/samples/awk/awk06.cpp
@@ -37,6 +37,7 @@ static int run_awk (QSE::StdAwk& awk)
 		"function add (a, b) { return a + b }\n"
 		"function mul (a, b) { return a * b }\n"
 		"function div (a, b) { return a / b }\n"
+		"function sine (a) { return sin(a) }\n"
 	);
 
 	QSE::StdAwk::SourceString in (script);
@@ -52,16 +53,25 @@ static int run_awk (QSE::StdAwk& awk)
 
 	// ret = add (-20, 51) 
 	QSE::StdAwk::Value ret;
-	if (awk.call (QSE_T("add"), &ret, arg, QSE_COUNTOF(arg)) <= -1) return -1;
+	if (awk.call (QSE_T("add"), &ret, arg, 2) <= -1) return -1;
 
 	// ret = mul (ret, 51);
 	arg[0] = ret;
-	if (awk.call (QSE_T("mul"), &ret, arg, QSE_COUNTOF(arg)) <= -1) return -1;
+	if (awk.call (QSE_T("mul"), &ret, arg, 2) <= -1) return -1;
 
 	// ret = div (ret, 2);
 	arg[0] = ret;
 	if (arg[1].setReal (run, 2) <= -1) return -1;
-	if (awk.call (QSE_T("div"), &ret, arg, QSE_COUNTOF(arg)) <= -1) return -1;
+	if (awk.call (QSE_T("div"), &ret, arg, 2) <= -1) return -1;
+
+	// output the result in various types
+	qse_printf (QSE_T("RESULT: (int) [%lld]\n"), (long long)ret.toInt());
+	qse_printf (QSE_T("        (real) [%Lf]\n"), (long double)ret.toReal());
+	qse_printf (QSE_T("        (str) [%s]\n"), ret.toStr(QSE_NULL));
+
+	// ret = sine (ret);
+	arg[0] = ret;
+	if (awk.call (QSE_T("sine"), &ret, arg, 1) <= -1) return -1;
 
 	// output the result in various types
 	qse_printf (QSE_T("RESULT: (int) [%lld]\n"), (long long)ret.toInt());