RFC2616 defines #rules as:

#rule
      A construct "#" is defined, similar to "*", for defining lists of
      elements. The full form is "<n>#<m>element" indicating at least
      <n> and at most <m> elements, each separated by one or more commas
      (",") and OPTIONAL linear white space (LWS). This makes the usual
      form of lists very easy; a rule such as
         ( *LWS element *( *LWS "," *LWS element ))
      can be shown as
         1#element

It also defines Linear White Space (LWS) as:
   LWS            = [CRLF] 1*( SP | HT )


The actual implementation only accepts SP (Space) and not HT (Horizontal Tab) when parsing cache related header fields (i.e. "Vary", "Cache-Control" and "Pragma")

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1710723 13f79535-47bb-0310-9956-ffa450edef68

CHANGES

@@ -1,6 +1,9 @@
                                                          -*- coding: utf-8 -*-
 Changes with Apache 2.5.0
 
+  *) mod_cache: Accept HT (Horizontal Tab) when parsing cache related header
+     fields as described in RFC2616. [Christophe Jaillet]
+
   *) htpasswd/htdigest: Disable support for bcrypt on EBCDIC platforms. 
      apr-util's bcrypt implementation doesn't tolerate EBCDIC.
 

modules/cache/cache_util.h

@@ -99,7 +99,7 @@ extern "C" {
 #define CACHE_LOCKNAME_KEY "mod_cache-lockname"
 #define CACHE_LOCKFILE_KEY "mod_cache-lockfile"
 #define CACHE_CTX_KEY "mod_cache-ctx"
-#define CACHE_SEPARATOR ",   "
+#define CACHE_SEPARATOR ", \t"
 
 /**
  * cache_util.c