--- checkdoc.el.~1.80.~	2009-11-09 08:46:10.000000000 +1100
+++ checkdoc.el	2009-11-09 09:33:33.000000000 +1100
@@ -334,12 +334,9 @@
   ;; "[.!?]" is for noun at end of a sentence, since those chars
   ;; are symbol syntax in emacs-lisp-mode and so don't match \\_>.
   ;; The \" allows it to be the last sentence in a docstring too.
-  (let ((expr "\\_<\\(")
-	(l checkdoc-proper-noun-list))
-    (while l
-      (setq expr (concat expr (car l) (if (cdr l) "\\|" ""))
-	    l (cdr l)))
-    (concat expr "\\)\\(\\_>\\|[.!?][ \t\n\"]\\)"))
+  (concat "\\_<"
+	  (regexp-opt checkdoc-proper-noun-list t)
+	  "\\(\\_>\\|[.!?][ \t\n\"]\\)")
   "Regular expression derived from `checkdoc-proper-noun-regexp'.")
 
 (defvar checkdoc-common-verbs-regexp nil