How do I congiure to deny funny url accesses?

Hi! Need help on configuration.

        acl allowed_addr src xxx.xxx.xxx.0/255.255.255.0
        acl for_our_eyes_only url_regex ^http://foo\.co\.jp\.*

        http_access allow for_our_eyes_only allowed_addr
        http_access deny for_our_eyes_only all

I set the above to deny hosts other than "allowed_addr"
from accessing URL http://foo.co.jp/whatever

When forbidden hosts tries to access URL "http://foo.co.jp/",
They get denied.
When they try "http://\foo.co.jp/" they get their pages..
Placing a backslash "\" allowes to bypass the rules.

What can I do to prevent it?
Are there any other character that allows such things?

I am using squid version:
Squid Cache: Version 1.0.18

Note: I do not belong the ML.
      Please cc: toku@ksp.nis.nec.co.jp
===================--------------------===================
Seiji Tokunaga (toku@ksp.nis.nec.co.jp)
NEC Informatec Systems, NSI Div., Network Integration Dept.
  TEL: 044-856-8481 FAX: 044-856-2273
  NEC TEL: 272-5607 FAX: 272-5649 MAIL:272-5600
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Received on Fri Jan 31 1997 - 01:30:35 MST