* lisp/progmodes/perl-mode.el (perl-syntax-propertize-special-constructs):

Don't move backward, so as not to fall in an inf-loop.

Fixes: debbugs:7736

lisp/ChangeLog

 2011-01-24  Stefan Monnier  <monnier@iro.umontreal.ca>
 
+	* progmodes/perl-mode.el (perl-syntax-propertize-special-constructs):
+	Don't move backward, so as not to fall in an inf-loop (bug#7736).
+
 	* progmodes/ruby-mode.el (ruby-syntax-propertize-function): (bug#7735)
 	Handle ?" and friends differently (e.g. don't use backrefs).
 

lisp/progmodes/perl-mode.el

@@ -360,7 +360,8 @@ The expansion is entirely correct because it uses the C preprocessor."
      (t
       ;; This is regexp like quote thingy.
       (setq char (char-after (nth 8 state)))
-      (let ((twoargs (save-excursion
+      (let ((startpos (point))
+            (twoargs (save-excursion
                        (goto-char (nth 8 state))
                        (skip-syntax-backward " ")
                        (skip-syntax-backward "w")
@@ -384,7 +385,8 @@ The expansion is entirely correct because it uses the C preprocessor."
 			  (goto-char (1+ (nth 8 state)))
 			  (up-list 1)
 			  t)
-		      (scan-error nil))
+                      ;; In case of error, make sure we don't move backward.
+		      (scan-error (goto-char startpos) nil))
 		  (not (or (nth 8 (parse-partial-sexp
 				   (point) limit nil nil state 'syntax-table))
 			   ;; If we have a self-paired opener and a twoargs