i think you've got it. i changed my test script from:

#!/usr/bin/perl
use CGI;
my $cgi = new CGI();
print $cgi->header();
foreach my $key (keys %ENV) {
    print "$key: $ENV{$key}<br />\n";
}
[download]

to:

#!/usr/bin/perl
use Apache;
my $r = Apache->request;
$r->content_type("text/html");
$r->send_http_header;
foreach my $key (keys %ENV) {
    print "$key: $ENV{$key}<br />\n";
}
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and it seems to work now.

do you know of any way to make it work with the former style. i usually take as much advantage of Registry's CGI emulation as possible so i can run scripts as either CGI or Registry. i know i can just put:

if ($ENV{MOD_PERL}) {
    use Apache;
    my $r = Apache->request;
    $r->content_type("text/html");
    $r->send_http_header;
} else {
    print $cgi->header();
}
[download]

into everything, but i'd rather not have to retrofit all my apps just to make them filterable. at least i know that if i upgrade to apache2, i can make anything filterable with the native filtering API. :)

You could set the content-type in your httpd.conf, either by file extension or with a directive inside your Location block. A better solution would be modifying Apache::Filter so it notices when you have already sent headers.