Index: doc/string.n
==================================================================
--- doc/string.n
+++ doc/string.n
@@ -16,10 +16,25 @@
 .BE
 .SH DESCRIPTION
 .PP
 Performs one of several string operations, depending on \fIoption\fR.
 The legal \fIoption\fRs (which may be abbreviated) are:
+.TP
+\fBstring cat\fR ?\fIstring1\fR? ?\fIstring2...\fR?
+.VS 8.6.2
+Concatenate the given \fIstring\fRs just like placing them directly
+next to each other and return the resulting compound string.  If no
+\fIstring\fRs are present, the result is an empty string.
+.RS
+.PP
+This primitive is occasionally handier than juxtaposition of strings
+when mixed quoting is wanted, or when the aim is to return the result
+of a concatenation without resorting to \fBreturn\fR \fB\-level 0\fR,
+and is more efficient than building a list of arguments and using
+\fBjoin\fR with an empty join string.
+.RE
+.VE
 .TP
 \fBstring compare\fR ?\fB\-nocase\fR? ?\fB\-length\fI length\fR? \fIstring1 string2\fR
 .
 Perform a character-by-character comparison of strings \fIstring1\fR
 and \fIstring2\fR.  Returns \-1, 0, or 1, depending on whether

Index: generic/tclCmdMZ.c
==================================================================
--- generic/tclCmdMZ.c
+++ generic/tclCmdMZ.c
@@ -2836,10 +2836,63 @@
 }
 
 /*
  *----------------------------------------------------------------------
  *
+ * StringCatCmd --
+ *
+ *	This procedure is invoked to process the "string cat" Tcl command.
+ *	See the user documentation for details on what it does.
+ *
+ * Results:
+ *	A standard Tcl result.
+ *
+ * Side effects:
+ *	See the user documentation.
+ *
+ *----------------------------------------------------------------------
+ */
+
+static int
+StringCatCmd(
+    ClientData dummy,		/* Not used. */
+    Tcl_Interp *interp,		/* Current interpreter. */
+    int objc,			/* Number of arguments. */
+    Tcl_Obj *const objv[])	/* Argument objects. */
+{
+    int i;
+    Tcl_Obj *objResultPtr;
+
+    if (objc < 2) {
+	/*
+	 * If there are no args, the result is an empty object.
+	 * Just leave the preset empty interp result.
+	 */
+	return TCL_OK;
+    }
+    if (objc == 2) {
+	/*
+	 * Other trivial case, single arg, just return it.
+	 */
+	Tcl_SetObjResult(interp, objv[1]);
+	return TCL_OK;
+    }
+    objResultPtr = objv[1];
+    if (Tcl_IsShared(objResultPtr)) {
+	objResultPtr = Tcl_DuplicateObj(objResultPtr);
+    }
+    for(i = 2;i < objc;i++) {
+	Tcl_AppendObjToObj(objResultPtr, objv[i]);
+    }
+    Tcl_SetObjResult(interp, objResultPtr);
+    
+    return TCL_OK;
+}
+
+/*
+ *----------------------------------------------------------------------
+ *
  * StringBytesCmd --
  *
  *	This procedure is invoked to process the "string bytelength" Tcl
  *	command. See the user documentation for details on what it does. Note
  *	that this command only functions correctly on properly formed Tcl UTF
@@ -3328,10 +3381,11 @@
 TclInitStringCmd(
     Tcl_Interp *interp)		/* Current interpreter. */
 {
     static const EnsembleImplMap stringImplMap[] = {
 	{"bytelength",	StringBytesCmd,	TclCompileBasic1ArgCmd, NULL, NULL, 0},
+	{"cat",		StringCatCmd,	TclCompileStringCatCmd, NULL, NULL, 0},
 	{"compare",	StringCmpCmd,	TclCompileStringCmpCmd, NULL, NULL, 0},
 	{"equal",	StringEqualCmd,	TclCompileStringEqualCmd, NULL, NULL, 0},
 	{"first",	StringFirstCmd,	TclCompileStringFirstCmd, NULL, NULL, 0},
 	{"index",	StringIndexCmd,	TclCompileStringIndexCmd, NULL, NULL, 0},
 	{"is",		StringIsCmd,	TclCompileStringIsCmd, NULL, NULL, 0},

Index: generic/tclCompCmdsSZ.c
==================================================================
--- generic/tclCompCmdsSZ.c
+++ generic/tclCompCmdsSZ.c
@@ -265,10 +265,82 @@
  *	Instructions are added to envPtr to execute the "string" command at
  *	runtime.
  *
  *----------------------------------------------------------------------
  */
+
+int
+TclCompileStringCatCmd(
+    Tcl_Interp *interp,		/* Used for error reporting. */
+    Tcl_Parse *parsePtr,	/* Points to a parse structure for the command
+				 * created by Tcl_ParseCommand. */
+    Command *cmdPtr,		/* Points to defintion of command being
+				 * compiled. */
+    CompileEnv *envPtr)		/* Holds resulting instructions. */
+{
+    int i, numWords = parsePtr->numWords, numArgs;
+    Tcl_Token *wordTokenPtr;
+    Tcl_Obj *obj, *folded;
+    DefineLineInformation;	/* TIP #280 */
+
+    /* Trivial case, no arg */
+
+    if (numWords<2) {
+	PushStringLiteral(envPtr, "");
+	return TCL_OK;
+    }
+	
+    /* General case: issue CONCAT1's (by chunks of 254 if needed), folding
+       contiguous constants along the way */
+
+    numArgs = 0;
+    folded = NULL;
+    wordTokenPtr = TokenAfter(parsePtr->tokenPtr);
+    for (i = 1; i < numWords; i++) {
+	obj = Tcl_NewObj();
+	if (TclWordKnownAtCompileTime(wordTokenPtr, obj)) {
+	    if (folded) {
+		Tcl_AppendObjToObj(folded, obj);
+		Tcl_DecrRefCount(obj);
+	    } else {
+		folded = obj;
+	    }
+	} else {
+	    Tcl_DecrRefCount(obj);
+	    if (folded) {
+		int len;
+		const char *bytes = Tcl_GetStringFromObj(folded, &len);
+		
+		PushLiteral(envPtr, bytes, len);
+		Tcl_DecrRefCount(folded);
+		folded = NULL;
+		numArgs ++;
+	    }
+	    CompileWord(envPtr, wordTokenPtr, interp, i);
+	    numArgs ++;
+	    if (numArgs >= 254) { /* 254 to take care of the possible +1 of "folded" above */
+		TclEmitInstInt1(INST_STR_CONCAT1, 254, envPtr);
+		numArgs -= 253;	/* concat pushes 1 obj, the result */
+	    }
+	}
+	wordTokenPtr = TokenAfter(wordTokenPtr);
+    }
+    if (folded) {
+	int len;
+	const char *bytes = Tcl_GetStringFromObj(folded, &len);
+	
+	PushLiteral(envPtr, bytes, len);
+	Tcl_DecrRefCount(folded);
+	folded = NULL;
+	numArgs ++;
+    }
+    if (numArgs > 1) {
+	TclEmitInstInt1(INST_STR_CONCAT1, numArgs, envPtr);
+    }
+
+    return TCL_OK;
+}
 
 int
 TclCompileStringCmpCmd(
     Tcl_Interp *interp,		/* Used for error reporting. */
     Tcl_Parse *parsePtr,	/* Points to a parse structure for the command

Index: generic/tclInt.h
==================================================================
--- generic/tclInt.h
+++ generic/tclInt.h
@@ -3643,10 +3643,13 @@
 MODULE_SCOPE int	TclCompileReturnCmd(Tcl_Interp *interp,
 			    Tcl_Parse *parsePtr, Command *cmdPtr,
 			    struct CompileEnv *envPtr);
 MODULE_SCOPE int	TclCompileSetCmd(Tcl_Interp *interp,
 			    Tcl_Parse *parsePtr, Command *cmdPtr,
+			    struct CompileEnv *envPtr);
+MODULE_SCOPE int	TclCompileStringCatCmd(Tcl_Interp *interp,
+			    Tcl_Parse *parsePtr, Command *cmdPtr,
 			    struct CompileEnv *envPtr);
 MODULE_SCOPE int	TclCompileStringCmpCmd(Tcl_Interp *interp,
 			    Tcl_Parse *parsePtr, Command *cmdPtr,
 			    struct CompileEnv *envPtr);
 MODULE_SCOPE int	TclCompileStringEqualCmd(Tcl_Interp *interp,

Index: tests/string.test
==================================================================
--- tests/string.test
+++ tests/string.test
@@ -28,11 +28,11 @@
 # Used for constraining memory leak tests
 testConstraint memory [llength [info commands memory]]
 
 test string-1.1 {error conditions} {
     list [catch {string gorp a b} msg] $msg
-} {1 {unknown or ambiguous subcommand "gorp": must be bytelength, compare, equal, first, index, is, last, length, map, match, range, repeat, replace, reverse, tolower, totitle, toupper, trim, trimleft, trimright, wordend, or wordstart}}
+} {1 {unknown or ambiguous subcommand "gorp": must be bytelength, cat, compare, equal, first, index, is, last, length, map, match, range, repeat, replace, reverse, tolower, totitle, toupper, trim, trimleft, trimright, wordend, or wordstart}}
 test string-1.2 {error conditions} {
     list [catch {string} msg] $msg
 } {1 {wrong # args: should be "string subcommand ?arg ...?"}}
 
 test string-2.1 {string compare, too few args} {
@@ -52,11 +52,11 @@
 } {1 {wrong # args: should be "string compare ?-nocase? ?-length int? string1 string2"}}
 test string-2.6 {string compare} {
     string compare abcde abdef
 } -1
 test string-2.7 {string compare, shortest method name} {
-    string c abcde ABCDE
+    string co abcde ABCDE
 } 1
 test string-2.8 {string compare} {
     string compare abcde abcde
 } 0
 test string-2.9 {string compare with length} {
@@ -79,11 +79,11 @@
 } 1
 test string-2.13 {string compare -nocase} {
     string compare -nocase abcde abdef
 } -1
 test string-2.14 {string compare -nocase} {
-    string c -nocase abcde ABCDE
+    string compare -nocase abcde ABCDE
 } 0
 test string-2.15 {string compare -nocase} {
     string compare -nocase abcde abcde
 } 0
 test string-2.16 {string compare -nocase with length} {
@@ -1511,11 +1511,11 @@
 test string-20.1 {string trimright errors} {
     list [catch {string trimright} msg] $msg
 } {1 {wrong # args: should be "string trimright string ?chars?"}}
 test string-20.2 {string trimright errors} {
     list [catch {string trimg a} msg] $msg
-} {1 {unknown or ambiguous subcommand "trimg": must be bytelength, compare, equal, first, index, is, last, length, map, match, range, repeat, replace, reverse, tolower, totitle, toupper, trim, trimleft, trimright, wordend, or wordstart}}
+} {1 {unknown or ambiguous subcommand "trimg": must be bytelength, cat, compare, equal, first, index, is, last, length, map, match, range, repeat, replace, reverse, tolower, totitle, toupper, trim, trimleft, trimright, wordend, or wordstart}}
 test string-20.3 {string trimright} {
     string trimright "    XYZ      "
 } {    XYZ}
 test string-20.4 {string trimright} {
     string trimright "   "
@@ -1570,11 +1570,11 @@
     string wordend "\uc700\uc700 abc" 8
 } 6
 
 test string-22.1 {string wordstart} {
     list [catch {string word a} msg] $msg
-} {1 {unknown or ambiguous subcommand "word": must be bytelength, compare, equal, first, index, is, last, length, map, match, range, repeat, replace, reverse, tolower, totitle, toupper, trim, trimleft, trimright, wordend, or wordstart}}
+} {1 {unknown or ambiguous subcommand "word": must be bytelength, cat, compare, equal, first, index, is, last, length, map, match, range, repeat, replace, reverse, tolower, totitle, toupper, trim, trimleft, trimright, wordend, or wordstart}}
 test string-22.2 {string wordstart} {
     list [catch {string wordstart a} msg] $msg
 } {1 {wrong # args: should be "string wordstart string index"}}
 test string-22.3 {string wordstart} {
     list [catch {string wordstart a b c} msg] $msg
@@ -1966,10 +1966,34 @@
 } {}
 test string-28.13 {tcl::prefix longest} {
     # Test UTF8 handling
     tcl::prefix longest {ax\x90 bep ax\x91} a
 } ax
+
+test string-29.1 {string cat, no arg} {
+    string cat
+} ""
+test string-29.2 {string cat, single arg} {
+    set x FOO
+    string compare $x [string cat $x]
+} 0
+test string-29.3 {string cat, two args} {
+    set x FOO
+    string compare $x$x [string cat $x $x]
+} 0
+test string-29.4 {string cat, many args} {
+    set x FOO
+    set n 260
+    set xx [string repeat $x $n]
+    set vv [string repeat {$x} $n]
+    set vvs [string repeat {$x } $n]
+    set r1 [string compare $xx [subst $vv]]
+    set r2 [string compare $xx [eval "string cat $vvs"]]
+    list $r1 $r2
+} {0 0}
+
+
 
 # cleanup
 rename MemStress {}
 catch {rename foo {}}
 ::tcltest::cleanupTests

Index: tests/stringComp.test
==================================================================
--- tests/stringComp.test
+++ tests/stringComp.test
@@ -44,11 +44,11 @@
 }
 
 test stringComp-1.1 {error conditions} {
     proc foo {} {string gorp a b}
     list [catch {foo} msg] $msg
-} {1 {unknown or ambiguous subcommand "gorp": must be bytelength, compare, equal, first, index, is, last, length, map, match, range, repeat, replace, reverse, tolower, totitle, toupper, trim, trimleft, trimright, wordend, or wordstart}}
+} {1 {unknown or ambiguous subcommand "gorp": must be bytelength, cat, compare, equal, first, index, is, last, length, map, match, range, repeat, replace, reverse, tolower, totitle, toupper, trim, trimleft, trimright, wordend, or wordstart}}
 test stringComp-1.2 {error conditions} {
     proc foo {} {string}
     list [catch {foo} msg] $msg
 } {1 {wrong # args: should be "string subcommand ?arg ...?"}}
 test stringComp-1.3 {error condition - undefined method during compile} {
@@ -208,11 +208,11 @@
 	-returnCodes $tcode -result $tresult
 }
 
 # need a few extra tests short abbr cmd
 test stringComp-3.1 {string compare, shortest method name} {
-    proc foo {} {string c abcde ABCDE}
+    proc foo {} {string co abcde ABCDE}
     foo
 } 1
 test stringComp-3.2 {string equal, shortest method name} {
     proc foo {} {string e abcde ABCDE}
     foo
@@ -733,14 +733,48 @@
 ## string trim*
 ## not yet bc
 
 ## string word*
 ## not yet bc
+
+## string cat
+test stringComp-29.1 {string cat, no arg} {
+    proc foo {} {string cat}
+    foo
+} ""
+test stringComp-29.2 {string cat, single arg} {
+    proc foo {} {
+	set x FOO
+	string compare $x [string cat $x]
+    }
+    foo
+} 0
+test stringComp-29.3 {string cat, two args} {
+    proc foo {} {
+	set x FOO
+	string compare $x$x [string cat $x $x]
+    }
+    foo
+} 0
+test stringComp-29.4 {string cat, many args} {
+    proc foo {} {
+	set x FOO
+	set n 260
+	set xx [string repeat $x $n]
+	set vv [string repeat {$x} $n]
+	set vvs [string repeat {$x } $n]
+	set r1 [string compare $xx [subst $vv]]
+	set r2 [string compare $xx [eval "string cat $vvs"]]
+	list $r1 $r2
+    }
+    foo
+} {0 0}
+
 
 # cleanup
 catch {rename foo {}}
 ::tcltest::cleanupTests
 return
 
 # Local Variables:
 # mode: tcl
 # End: