Getting %ENV into a filter

[Mike Whitaker]

I'm replacing a somewhat flaky use of mod_layout with a 
PerlOutputFilterHandler  - it's all a little bit ugly, but...

Basically:
I have a RewriteRule whose major function is to set an ENV variable 
(PACKAGE) dependent on the Host: header before invoking a CGI.

The output of this CGI gets passed through a filter, viz:
        PerlModule Foo
        AddHandler cgi-script .cgi
        <Directory "/foo/cgi/">
                AllowOverride None
                Options ExecCGI -MultiViews +SymLinksIfOwnerMatch
                Order allow,deny
                Allow from all
                PerlOptions +SetupEnv
                PerlOutputFilterHandler Foo
        </Directory>
And then Foo.pm has a handler(), viz:
sub handler
{
        my $f = shift;
        $f->r->subprocess_env;
        my $p = $ENV{PACKAGE};
        ...
}
And I get:
[Mon Mar 14 12:25:24 2005] [error] [client 192.168.1.107] Can't locate 
object method "subprocess_env" via package "Apache::RequestRec" at 
Foo.pm line 22.

If I leave the subprocess_env call out, it all works except (obviously) 
%ENV doesn't get populated.

What am I missing?
(Debian apache2 2.0.53, mod_perl 1.999.20)