[Exim] Defining PIPE (perl) in /etc/aliases?

I am trying to define a way to get incoming e-mail into a Perl
script via the /path/to/program < $1 method in /etc/aliases --
however I keep seeing:

2003-01-23 23:41:28 18bvei-00005J-00 Neither the system_aliases
director nor the address_pipe transport set a uid for local
delivery of |/root/webmaster <$1

Any ideas about what I am missing or doing wrong?

Thx/Sx :]