However CGI.pm is heavily recommended because it is probably the best tool to do the job for lots of people who do a lot of CGI work, and it has been hammered on alot so we know it is robust. Professionals using it should understand the underlying protocol relatively well but not waste their time on things which are not central to the task at hand.
One of the most powerful things about Perl is the CPAN module network and being able to leverage off of the countless hours of time invested in this community resource by people around the world. While CPAN does not always have the answer, it often has some very good stuff so I often look there first, among other places. I learn and look at source code, usually, and do look for all tools available to enhance security because I have a responsibility to the person who is paying me to do it.
So while I applaud your enthusiasm for learning perl, I'd have to say that in general learning is one thing. Intentional ignorance is not defensible. There are very good reasons why seasoned programmers who are totally capable of doing what you did (and likely have done so many times) make a point of not doing so. Read tons, make your mistakes on your own time, and become a great programmer! We'll all use your modules if they do the job.