[SA 3.4.1] Are all Perl module dependencies necessary?

[Matteo Dessalvi <mt...@yahoo.it>]

Hi all.
I am running SA version 3.4.1 on Debian Jessie (from the backport archives). SA run through Amavis and so far I did not have any problem, nor with the classification orthe updates through sa-update. Following the advises on the SA wiki (https://wiki.apache.org/spamassassin/ImproveAccuracy), I just ran: "spamassassin -D --lint 2>&1 | grep -i failed"
and I got the following output:
[...]
Dec 10 11:47:20.731 [6060] dbg: diag: [...] module not installed: Digest::SHA1 ('require' failed)Dec 10 11:47:20.731 [6060] dbg: diag: [...] module not installed: Geo::IP ('require' failed)
Dec 10 11:47:20.731 [6060] dbg: diag: [...] module not installed: Net::CIDR::Lite ('require' failed)Dec 10 11:47:20.732 [6060] dbg: diag: [...] module not installed: LWP::UserAgent ('require' failed)Dec 10 11:47:20.732 [6060] dbg: diag: [...] module not installed: Encode::Detect::Detector ('require' failed)
Dec 10 11:47:20.732 [6060] dbg: diag: [...] module not installed: Net::Patricia ('require' failed)
Despite the 'require failed' messages, how much of these plugins are actually used by SA? Are those missing plugins preventing some of the rules from triggering oraffecting the scoring process in any sensible way? Or they are basically bypassed by the fact that SA is invoked through Amavis via the 'Mail::SpamAssassin' module?

I went ahead and install all the missing Perl modules through additional packages but it would be nice to know why these requirements seems not to affect SA. 
Can anybody explain it to me or point me to the docs/code commits/bug reports/mailing list thread/ related to this?

Thanks in advance!
Best regards,Matteo