Personally, I learned Perl the way that I learn most technical subjects, by reading and practicing. I have for the past 40+ years scheduled an hour before Work to sit with a cup of coffee and my current technical document. I read, I take notes, I write short codes that illustrate what I have been reading, and I drink some more coffee.

When I learned Perl I started with the Llama (Learning Perl), continued with the Camel (Programming Perl) and then the Big Horn Sheep (the Perl Cookbook) and the Timber Wolf (Algorithms in Perl). It took about three years.

I have used the same tactic with other Technical subjects: languages (Python, Javascript, Haskell), operating systems (Unix, Linux, FreeBSD, Solaris, zOS), tools (Vim/Vi, Nagios, Apache, SQL, shell), etc.

This is the way that I learn. I don't really know anything, I just remember where I can look it up. It's a principal I stole from Unix, keep only the bare minimum code necessary in main memory, page everything else out to auxillary....