[exim] problems with exiscan-acl

Hello,

my system is:
debian sarge
Exim version 4.34 #1 built 05-Jan-2005 11:07:49
Contains exiscan-acl patch revision 21 (c) Tom Kistner

my testentries în acl_smtp_data:

warn
condition = true
logwrite = :main: test found_extension = ***$found_extension***

warn
condition = true
logwrite = :main: test mime_filename = ***$found_extension***

but there is nothing between the asterisks?

whats going wrong?

Thanks for any hint
Peter