Hi Bowie,
As far as I know, the module lookup is a function of the Perl install. In order to keep your current stuff along with the new stuff, you would need a second install of Perl.
Why do you want to keep the old modules? I can understand not wanting to upgrade Perl itself, but unless you've got something that relies on Net::DNS that you are worried about breaking, I'd say just upgrade them.
I don't want to interfere with Debians packages. In amavisd-new, I installed the packages manually with
perl Makefile.PL LIB=/usr/local/share/amavisd-new PREFIX=/usr/local/share/amavisd-new
I modified the amavisd-new binary with use lib qw(/usr/local/share/amavisd-new);
and it works.,
Florian
