=== modified file 'lisp/subr.el'
--- lisp/subr.el	2013-02-09 16:20:29 +0000
+++ lisp/subr.el	2013-03-06 17:51:43 +0000
@@ -2670,9 +2670,12 @@ directory if it does not exist."
   "Return non-nil if the current buffer is narrowed."
   (/= (- (point-max) (point-min)) (buffer-size)))
 
-(defun find-tag-default ()
+(defun find-tag-default (&optional regexp-p)
   "Determine default tag to search for, based on text at point.
-If there is no plausible default, return nil."
+If there is no plausible default, return nil.
+
+When optional argument REGEXP-P is nil, return a regexp that
+matches tag as a symbol."
   (let (from to bound)
     (when (or (progn
 		;; Look at text around `point'.
@@ -2695,7 +2698,9 @@ If there is no plausible default, return
 		     (< (setq from (point)) bound)
 		     (skip-syntax-forward "w_")
 		     (setq to (point)))))
-      (buffer-substring-no-properties from to))))
+      (let ((tag (buffer-substring-no-properties from to)))
+	(if (not regexp-p) tag
+	  (format "\\_<%s\\_>" (regexp-quote tag)))))))
 
 (defun play-sound (sound)
   "SOUND is a list of the form `(sound KEYWORD VALUE...)'.