If your amavisd-new suddenly doesn’t want to start anymore, reporting that some required Perl modules aren’t installed allegedly, then maybe the cause is something like
# locate -r Compress.*Zlib.pm
/usr/lib/perl5/Compress/Raw/Zlib.pm
/usr/share/perl5/Compress/Zlib.pm
/usr/local/lib/perl/5.8.8/Compress/Raw/Zlib.pm
/usr/local/share/perl/5.8.8/Compress/Zlib.pm
Took me 2 hours. I need that CPAN stuff apart from Debian at least for Geo::IPfree to map IPs to country names for my web statistics.