Perl5. Some version of perl5 is available by default on just about everything and can be counted on in a similar manner as counting on awk to be there for you.
I'm not going to defend Perl's readability, there are many opus's online in both directions. Suffice it to say that Perl is still a really good tool for certain $jobs.
For learning Perl, I used this: https://qntm.org/perl_en followed by some trial and error, followed by the book Modern Perl, then Higher Order Perl. glhf! Perl hacking is a blast
I'm not going to defend Perl's readability, there are many opus's online in both directions. Suffice it to say that Perl is still a really good tool for certain $jobs.
For learning Perl, I used this: https://qntm.org/perl_en followed by some trial and error, followed by the book Modern Perl, then Higher Order Perl. glhf! Perl hacking is a blast