I've been practicing programming in Perl today, using exercises from practicepython.org...

LOL Are you a masochist?

Go to the local library and get a copy of https://www.amazon.com/Learning-Perl-Randal-L-Schwartz/dp/1449303587, or an older edition of the Learning Perl book. You can read it cover to cover, or try to use it as a reference book. When you are done with that, you can try Intermediate Perl: Beyond The Basics of Learning Perl 2nd Edition or https://www.amazon.com/Beginning-Perl-Curtis-Poe/dp/1118013840

Or, one can learn online. For example, this popped up when I Googled "perl arrays": https://perlmaven.com/perl-arrays.

Try things out. If they don't work, start a thread at PerlMonks. Weekends tend to be slow. During the week, there are more people here. There is so much experience in this community that it is unbelieveable.

You can try this area of PerlMonks: Tutorials.

Then, there is the Perl documentation. The easiest way to get to it is on the Internet. For example, http://perldoc.perl.org/perlintro.html#Perl-variable-types. However, these tend to be rather dense, rather than pedagogical.