About the Perl book, I think I'll skip that one. I rather focus on Python (as it's extremely popular) and simple shell scripts (a good book for this one would be appreciated).
I'm mostly writing Python these days. When I worked at Sun many of the engineers praised Perl, so early on when I deciding what to do for fun Perl was the obvious choice. I've not really done any Perl since maybe 2015.
I kinda clicked with Perl, it felt like shell++. Python still jars with me a bit.
For shell scripting, I generally use a mix of man pages and UNIX in a nutshell which is showing it's age a bit! @freebsdfrau on Twitter has started putting together a book on gitbooks called Serious Shell Programming. I can't comment on it personally, but I've seen some good feedback on Twitter a while ago.