Below is true in Switzerland and neighbouring France, but I believe it's true in large parts of the world.

There are many proffesional training courses for Perl, but those I've seen have all been beginners courses. If your friend is already skilled in C, C++, etc. it is probably easier for him to pick up Learing Perl. He will learn more and quicker from reading the book than spending three days learning the basics of Perl in a commercial training (in this part of Europe).

Since Perl comes very much from the UNIX world, there is one thing that directly comes to mind: Read The Fine Manual.

My personal experience is that Perl is a language you have to practice to learn. Of course, exchanging ideas and experiences with other Perl programmers (Perl Monks?) helps a lot. But reading, trying, practicing are my keywords.