diff -pruN mutt-1.3.25.orig/doc/manual.sgml.head mutt-1.3.25/doc/manual.sgml.head
--- mutt-1.3.25.orig/doc/manual.sgml.head	Tue Nov  6 11:33:24 2001
+++ mutt-1.3.25/doc/manual.sgml.head	Sat Jan 12 03:11:40 2002
@@ -1718,6 +1718,7 @@ messages:
 ~x EXPR         messages which contain EXPR in the `References' field
 ~y EXPR         messages which contain EXPR in the `X-Label' field
 ~z [MIN]-[MAX]  messages with a size in the range MIN to MAX *)
+~=		duplicated messages (see $duplicate_threads)
 </verb></tscreen>
 
 Where EXPR, USER, ID, and SUBJECT are 
diff -pruN mutt-1.3.25.orig/mutt.h mutt-1.3.25/mutt.h
--- mutt-1.3.25.orig/mutt.h	Thu Dec 13 13:10:49 2001
+++ mutt-1.3.25/mutt.h	Sat Jan 12 03:11:40 2002
@@ -201,6 +201,7 @@ enum
   M_FROM,
   M_DATE,
   M_DATE_RECEIVED,
+  M_DUPLICATED,
   M_ID,
   M_BODY,
   M_HEADER,
diff -pruN mutt-1.3.25.orig/pattern.c mutt-1.3.25/pattern.c
--- mutt-1.3.25.orig/pattern.c	Mon Dec  3 11:17:57 2001
+++ mutt-1.3.25/pattern.c	Sat Jan 12 03:11:40 2002
@@ -90,6 +90,7 @@ Flags[] =
   { 'x', M_REFERENCE,		0,		eat_regexp },
   { 'y', M_XLABEL,		0,		eat_regexp },
   { 'z', M_SIZE,		0,		eat_range },
+  { '=', M_DUPLICATED,		0,		NULL },
   { 0 }
 };
 
@@ -1050,6 +1051,8 @@ mutt_pattern_exec (struct pattern_t *pat
 #endif
     case M_XLABEL:
       return (pat->not ^ (h->env->x_label && regexec (pat->rx, h->env->x_label, 0, NULL, 0) == 0));
+    case M_DUPLICATED:
+      return (pat->not ^ (h->thread && h->thread->duplicate_thread));
   }
   mutt_error (_("error: unknown op %d (report this error)."), pat->op);
   return (-1);
diff -pruN mutt-1.3.25.orig/PATCHES mutt-1.3.25/PATCHES
--- mutt-1.3.25.orig/PATCHES    Mon Nov 26 20:16:52 2001
+++ mutt-1.3.25/PATCHES Thu Dec  6 16:27:55 2001
@@ -1,0 +1 @@
+patch-1.3.25.cd.pattern_duplicates.1