Didn't help to learn how to hack Perl.

You already said that, what does that mean?

perlhack DESCRIPTION is

This document explains how Perl development works. It includes details about the Perl 5 Porters email list, the Perl repository, the Perlbug bug tracker, patch guidelines, and commentary on Perl development philosophy.

And perlhack does indeed teach that

So what do you mean?

FunkyMonk points you to perlguts, but that can't be what you're after, after all, perlhack points you to perlguts MORE READING FOR GUTS HACKERS