procmail regex help ... sometimes works, sometimes doesn't...

[George Sanders]

I have added a very standard, very common regex line to my .procmailrc to filter character sets I can't read:


UNREADABLE='[^?"]*big5|iso-2022-jp|ISO-2022-KR|euc-kr|gb2312|ks_c_5601-1987|ks_c_5601|3Deuc-kr|koi8'
:0:
* ^Content-Type:.*multipart
* B ?? $ ^Content-Type:.*^?.*charset="?($UNREADABLE)
unreadable_messages


I know that this works because my "unreadable_messages" mail file is now full of messages with headers like:


From: =?GB2312?B?xMLTq9Or?= <uigvrutit at heki.net>
Subject: =?GB2312?B?MjAxMMTqyMvBptfK1LS4w9bYytPKssO0?=
To: "me" <me at me.com>
Content-Type: text/html;
        charset="gb2312"


However, a lot of mail gets through to my inbox that matches:


From: "osdeiiftnvpp at gmail.com" <xjyfgzyjm at gmail.com>
Reply-To: "osdeiiftnvpp at gmail.com" <xjyfgzyjm at gmail.com>
Message-ID: <533pbxxy2oc>
To: me <me at me.com>
Subject: Fw: \xb8\xf2\xad\xe8\xa5X\xa8\xd3\xbd\xe6~\xb1o\xb4\xa9\xa9f\xaa\xb1\xb5L\xaeM\xa4\xba\xaeg\xb2n\xa7o
X-Mailer: inhalation
Organization: Microsoft Outlook Express 6.00.2462.0000
Mime-Version: 1.0
Content-Type: multipart/alternative;
        boundary="1-104247307-2712732737=:8213"
Status: RO
X-Status:
X-Keywords:
X-UID: 63502

--1-104247307-2712732737=:8213
Content-Type: text/plain; charset="big5"
Content-Transfer-Encoding: quoted-printable


However, "big5" is very clearly listed in my regex above, and as far as I can tell, this mail should match perfectly...

I cannot see why these "big5" emails are not matching my procmail regex ... is it obvious to anyone ?