acl rep_header Content_length does not work

["lopl" <lopl@xxxxxxxxxx>]

Dear
I need to use an acl that works with reply size.

better way( I found) is using following acl
acl aclname rep_header header-name [-i] any\.regex\.here # from 
squid.conf.default

changed to:

acl bigfiles rep_header Content-Length ^(1|2)?+[0-9]{0,6}?$

http_access deny bigfiles
http_access allow all

it does not work.why?:
all of smal and big files are allowed!!!


please help me.
Best
Pezhman