I tried the Apache2::RequestUtil->request and it didnt work as expected.

It should work. What happened?

The old version didnt use Apache::Registry but Apache::PerlRun.

That doesn't matter.

The browser offers me to download the file instead...

That usually means you aren't sending a header.

<Location /webnet>
SetHandler perl-script
PerlResponseHandler ModPerl::PerlRun
PerlHandler Apache::PerlRun
Options +ExecCGI
</Location>
[download]

Your PerlHandler setting should be removed. You may also want to PerlOptions +ParseHeaders

But mod_perl and mod_perl2 do not coexist on the same box, do they?

Sure they do. If you want to be especially careful, you can install a separate perl to use with mod_perl 2 so that none of the modules get installed in the main perl tree.