Glad to help!

How did it occur to you to use Data::Dumper and then use IPC::Run3? Why not anything else?

Because I've done a fair amount of research on the topic of calling external commands (see e.g. here), I knew that IPC::Run3 was likely to work best for you on Windows. Then, when debugging Unicode issues, one needs to see the data that Perl is storing (see also my post here) with nonprintable characters visualized, for which one needs to use a dumper module like Data::Dump, Data::Dumper with $Data::Dumper::Useqq=1;, or for difficult cases Devel::Peek.

how do I get better at understanding the CPAN docs?

I think this will come along with learning more about Perl. A lot of CPAN authors (including myself) will use terminology and idioms that they assume people know, so as you get better at Perl you'll recognize more and more of these. And in the meantime, you're always welcome to ask here!

What book would you suggest for someone like me who knows perl but wants to get much better acquainted with perl?

See my post here and threads like So what is your Perl book "Trilogy" anyway?