diff --git a/Build.sh b/Build.sh
index d75b15e..ec0d64c 100644
--- a/Build.sh
+++ b/Build.sh
@@ -1,5 +1,5 @@
 #!/bin/sh
-srcversion='$MirOS: src/bin/mksh/Build.sh,v 1.680 2015/07/05 15:45:16 tg Exp $'
+srcversion='$MirOS: src/bin/mksh/Build.sh,v 1.681 2015/07/06 17:48:28 tg Exp $'
 #-
 # Copyright (c) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
 #		2011, 2012, 2013, 2014, 2015
@@ -2645,9 +2645,6 @@ MKSH_NOPROSPECTOFWORK		disable jobs, co-processes, etc. (do not use)
 MKSH_NOPWNAM			skip PAM calls, for -static on glibc or Solaris
 MKSH_NO_CMDLINE_EDITING		disable command line editing code entirely
 MKSH_NO_DEPRECATED_WARNING	omit warning when deprecated stuff is run
-MKSH_NO_EXTERNAL_CAT		omit hack to skip cat builtin when flags passed
-MKSH_NO_EXTERNAL_REALPATH	same for realpath builtin
-MKSH_NO_EXTERNAL_RENAME		same for rename builtin
 MKSH_NO_LIMITS			omit ulimit code
 MKSH_NO_SIGSETJMP		define if sigsetjmp is broken or not available
 MKSH_NO_SIGSUSPEND		use sigprocmask+pause instead of sigsuspend
diff --git a/check.t b/check.t
index 34aa403..2b461d0 100644
--- a/check.t
+++ b/check.t
@@ -1,4 +1,4 @@
-# $MirOS: src/bin/mksh/check.t,v 1.698 2015/07/05 19:37:11 tg Exp $
+# $MirOS: src/bin/mksh/check.t,v 1.699 2015/07/06 17:48:29 tg Exp $
 # -*- mode: sh -*-
 #-
 # Copyright © 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
@@ -30,7 +30,7 @@
 # (2013/12/02 20:39:44) http://openbsd.cs.toronto.edu/cgi-bin/cvsweb/src/regress/bin/ksh/?sortby=date
 
 expected-stdout:
-	@(#)MIRBSD KSH R51 2015/07/05
+	@(#)MIRBSD KSH R51 2015/07/06
 description:
 	Check version of shell.
 stdin:
@@ -39,7 +39,7 @@ name: KSH_VERSION
 category: shell:legacy-no
 ---
 expected-stdout:
-	@(#)LEGACY KSH R51 2015/07/05
+	@(#)LEGACY KSH R51 2015/07/06
 description:
 	Check version of legacy shell.
 stdin:
@@ -8533,7 +8533,7 @@ description:
 	Ensure concatenating behaviour matches other shells
 stdin:
 	showargs() { for s_arg in "$@"; do echo -n "<$s_arg> "; done; echo .; }
-	#showargs 0 ""$@
+	showargs 0 ""$@
 	x=; showargs 1 "$x"$@
 	set A; showargs 2 "${@:+}"
 	n() { echo "$#"; }
@@ -8553,6 +8553,7 @@ stdin:
 	n "$@"
 	n "$@""$e"
 expected-stdout:
+	<0> <> .
 	<1> <> .
 	<2> <> .
 	2
@@ -8568,17 +8569,6 @@ expected-stdout:
 	0
 	1
 ---
-name: varexpand-null-3a
-description:
-	Ensure concatenating behaviour matches other shells
-	(currently broken cases)
-expected-fail: yes
-stdin:
-	showargs() { for s_arg in "$@"; do echo -n "<$s_arg> "; done; echo .; }
-	showargs 0 ""$@
-expected-stdout:
-	<0> <> .
----
 name: print-funny-chars
 description:
 	Check print builtin's capability to output designated characters
diff --git a/exec.c b/exec.c
index 3f8863c..bf8c4a8 100644
--- a/exec.c
+++ b/exec.c
@@ -23,7 +23,7 @@
 
 #include "sh.h"
 
-__RCSID("$MirOS: src/bin/mksh/exec.c,v 1.154 2015/07/05 15:45:17 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/exec.c,v 1.155 2015/07/06 17:48:31 tg Exp $");
 
 #ifndef MKSH_DEFAULT_EXECSHELL
 #define MKSH_DEFAULT_EXECSHELL	"/bin/sh"
@@ -551,6 +551,8 @@ comexec(struct op *t, struct tbl * volatile tp, const char **ap,
 			}
 			if ((tp = findcom(cp, FC_BI)) == NULL)
 				errorf("%s: %s: %s", Tbuiltin, cp, "not a builtin");
+			if (tp->type == CSHELL && tp->val.f == c_cat)
+				break;
 			continue;
 		} else if (tp->val.f == c_exec) {
 			if (ap[1] == NULL)
@@ -607,30 +609,19 @@ comexec(struct op *t, struct tbl * volatile tp, const char **ap,
 				subst_exstat = 0;
 				break;
 			}
-#if !defined(MKSH_NO_EXTERNAL_CAT) || \
-    !defined(MKSH_NO_EXTERNAL_REALPATH) || \
-    !defined(MKSH_NO_EXTERNAL_RENAME)
-		} else if (
-#ifndef MKSH_NO_EXTERNAL_CAT
-		    tp->val.f == c_cat ||
-#endif
-#ifndef MKSH_NO_EXTERNAL_REALPATH
-		    tp->val.f == c_realpath ||
-#endif
-#ifndef MKSH_NO_EXTERNAL_RENAME
-		    tp->val.f == c_rename ||
-#endif
-		    0) {
+		} else if (tp->val.f == c_cat) {
 			/* if we have any flags, do not use the builtin */
 			if (ap[1] && ap[1][0] == '-' && ap[1][1] != '\0' &&
 			    /* argument, begins with -, is not - or -- */
-			    (ap[1][1] != '-' || ap[1][2] != '\0'))
-				/* don't look for builtins or functions */
-				fcflags = FC_PATH;
-			else
-				/* go on, use the builtin */
-				break;
-#endif
+			    (ap[1][1] != '-' || ap[1][2] != '\0')) {
+				struct tbl *ext_cat;
+
+				ext_cat = findcom(Tcat, FC_PATH | FC_FUNC);
+				if (ext_cat && (ext_cat->type != CTALIAS ||
+				    (ext_cat->flag & ISSET)))
+					tp = ext_cat;
+			}
+			break;
 		} else if (tp->val.f == c_trap) {
 			t->u.evalflags &= ~DOTCOMEXEC;
 			break;
@@ -710,6 +701,7 @@ comexec(struct op *t, struct tbl * volatile tp, const char **ap,
 
 	/* shell built-in */
 	case CSHELL:
+ do_call_builtin:
 		rv = call_builtin(tp, (const char **)ap, null, resetspec);
 		if (resetspec && tp->val.f == c_shift) {
 			l_expand->argc = l_assign->argc;
@@ -734,6 +726,11 @@ comexec(struct op *t, struct tbl * volatile tp, const char **ap,
 				break;
 			}
 			if (include(tp->u.fpath, 0, NULL, false) < 0) {
+				if (!strcmp(cp, Tcat)) {
+ no_cat_in_FPATH:
+					tp = findcom(Tcat, FC_BI);
+					goto do_call_builtin;
+				}
 				warningf(true, "%s: %s %s %s: %s", cp,
 				    "can't open", "function definition file",
 				    tp->u.fpath, cstrerror(errno));
@@ -742,6 +739,8 @@ comexec(struct op *t, struct tbl * volatile tp, const char **ap,
 			}
 			if (!(ftp = findfunc(cp, hash(cp), false)) ||
 			    !(ftp->flag & ISSET)) {
+				if (!strcmp(cp, Tcat))
+					goto no_cat_in_FPATH;
 				warningf(true, "%s: %s %s", cp,
 				    "function not defined by", tp->u.fpath);
 				rv = 127;
diff --git a/funcs.c b/funcs.c
index 64c7d2f..1be28e4 100644
--- a/funcs.c
+++ b/funcs.c
@@ -38,7 +38,7 @@
 #endif
 #endif
 
-__RCSID("$MirOS: src/bin/mksh/funcs.c,v 1.276 2015/07/05 19:37:14 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/funcs.c,v 1.277 2015/07/06 17:48:32 tg Exp $");
 
 #if HAVE_KILLPG
 /*
@@ -99,7 +99,7 @@ const struct builtin mkshbuiltins[] = {
 	{Talias, c_alias},
 	{"*=break", c_brkcont},
 	{Tgbuiltin, c_builtin},
-	{"cat", c_cat},
+	{Tcat, c_cat},
 	{"cd", c_cd},
 	/* dash compatibility hack */
 	{"chdir", c_cd},
diff --git a/main.c b/main.c
index eecea60..64fa3dd 100644
--- a/main.c
+++ b/main.c
@@ -34,7 +34,7 @@
 #include <locale.h>
 #endif
 
-__RCSID("$MirOS: src/bin/mksh/main.c,v 1.294 2015/07/05 19:37:16 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/main.c,v 1.295 2015/07/06 17:48:34 tg Exp $");
 
 extern char **environ;
 
@@ -87,7 +87,7 @@ static const char *initcoms[] = {
 	NULL,
 	 /* this is what AT&T ksh seems to track, with the addition of emacs */
 	Talias, "-tU",
-	"cat", "cc", "chmod", "cp", "date", "ed", "emacs", "grep", "ls",
+	Tcat, "cc", "chmod", "cp", "date", "ed", "emacs", "grep", "ls",
 	"make", "mv", "pr", "rm", "sed", "sh", "vi", "who", NULL,
 	NULL
 };
diff --git a/mksh.1 b/mksh.1
index fb9666b..85dbda4 100644
--- a/mksh.1
+++ b/mksh.1
@@ -1,4 +1,4 @@
-.\" $MirOS: src/bin/mksh/mksh.1,v 1.372 2015/07/05 19:37:17 tg Exp $
+.\" $MirOS: src/bin/mksh/mksh.1,v 1.373 2015/07/06 17:48:35 tg Exp $
 .\" $OpenBSD: ksh.1,v 1.160 2015/07/04 13:27:04 feinerer Exp $
 .\"-
 .\" Copyright © 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
@@ -74,7 +74,7 @@
 .\" with -mandoc, it might implement .Mx itself, but we want to
 .\" use our own definition. And .Dd must come *first*, always.
 .\"
-.Dd $Mdocdate: July 5 2015 $
+.Dd $Mdocdate: July 6 2015 $
 .\"
 .\" Check which macro package we use, and do other -mdoc setup.
 .\"
@@ -3161,15 +3161,13 @@ If a
 is a single dash
 .Pq Sq -
 or absent, read from standard input.
-Unless compiled with
-.Dv MKSH_NO_EXTERNAL_CAT ,
-if any options are given, an external
-.Xr cat 1
-utility is invoked instead if called from the shell.
 For direct builtin calls, the
 .Tn POSIX
 .Fl u
 option is supported as a no-op.
+For calls from shell, if any options are given, an external
+.Xr cat 1
+utility is preferred over the builtin.
 .Pp
 .It Xo
 .Ic cd
@@ -3958,12 +3956,6 @@ it's also checked for existence and whether it is a directory; otherwise,
 returns 0 if the pathname either exists or can be created immediately,
 i.e. all but the last component exist and are directories.
 .Pp
-Unless compiled with
-.Dv MKSH_NO_EXTERNAL_REALPATH ,
-if any options are given and this is not a direct builtin call, an external
-.Xr realpath 1
-utility is invoked instead.
-.Pp
 .It Xo
 .Ic rename
 .Op Fl \-
@@ -3978,11 +3970,6 @@ This builtin is intended for emergency situations where
 .Pa /bin/mv
 becomes unusable, and directly calls
 .Xr rename 2 .
-Unless compiled with
-.Dv MKSH_NO_EXTERNAL_RENAME ,
-if any options are given and this is not a direct builtin call, an external
-.Xr rename 1
-utility is invoked instead.
 .Pp
 .It Ic return Op Ar status
 Returns from a function or
diff --git a/sh.h b/sh.h
index 74d4b57..23c7e5a 100644
--- a/sh.h
+++ b/sh.h
@@ -169,9 +169,9 @@
 #endif
 
 #ifdef EXTERN
-__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.733 2015/07/05 19:37:18 tg Exp $");
+__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.734 2015/07/06 17:48:37 tg Exp $");
 #endif
-#define MKSH_VERSION "R51 2015/07/05"
+#define MKSH_VERSION "R51 2015/07/06"
 
 /* arithmetic types: C implementation */
 #if !HAVE_CAN_INTTYPES
@@ -821,6 +821,7 @@ EXTERN const char T_typeset[] E_INIT("=typeset");
 #define Ttypeset	(T_typeset + 1)		/* "typeset" */
 EXTERN const char Talias[] E_INIT("alias");
 EXTERN const char Tunalias[] E_INIT("unalias");
+EXTERN const char Tcat[] E_INIT("cat");
 EXTERN const char Tsgset[] E_INIT("*=set");
 #define Tset		(Tsgset + 2)		/* "set" */
 EXTERN const char Tsgexport[] E_INIT("*=export");