What we've put in this book so far is the core of Perl, the part that every Perl user should understand. A few other techniques, while not obligatory, are still valuable tools to have in your toolbox. We've gathered the most important of those in this chapter.
Don't be misled by the title of the chapter; these techniques aren't more difficult to understand than the rest of the book. They are only "advanced" in the sense that they aren't necessary for beginners. The first time you read this book, you may want to skip (or skim) this chapter so you can get right to using Perl. Come back to it later when you're ready to get more out of Perl. Consider this entire chapter a huge footnote.[*]