Index: tclCmdMZ.c
===================================================================
--- tclCmdMZ.c	
+++ tclCmdMZ.c	
@@ -264,9 +264,12 @@
 	 * considered the start of the line. If for example the pattern {^} is
 	 * passed and -start is positive, then the pattern will not match the
 	 * start of the string unless the previous character is a newline.
+	 *
+	 * [SEBRES] offset > 0 is needless (boolean logic (offs == 0 || ...)), negative already checked above
+	 *   (offset < stringLength) prevents access violation for -start offsets greater as length.
 	 */
 
-	if ((offset == 0) || ((offset > 0) &&
+	if ((offset == 0) || ((offset < stringLength) &&
 		(Tcl_GetUniChar(objPtr, offset-1) == (Tcl_UniChar)'\n'))) {
 	    eflags = 0;
 	} else {
