I think everyone can agree that a module that adds a function you already have, like addition, is silly, and without a more concrete example it's hard to say much more about it. I'd consider nearly any use of CPAN modules to be justified if the module adds significant required functionality. 50 modules? sure, go ahead.
What's more interesting to me is how different your experience with Perl newbies seems to be from mine. When I was looking to hire a junior person, 99% of the people I talked to claiming to be Perl coders had barely even heard of CPAN. They had all used DBI, and maybe CGI, but when I asked them to name some favorite modules they were at a loss. Complete opposite of the module addiction you're describing here.