If you want to use MacPerl (the excellent port of Perl to MacOS, loaded with useful Mac-specific functions), you can do it one of two ways:
You can buy this book; or you you can poke around aimlessly for about two years learning, by trial and error (and guess, and crash), what is clearly laid out in this book.
Two years ago I was an already fairly experienced Perler, but with little experience with MacPerl. If I'd had this book two years ago, it would have saved me more time than I really even want to admit -- weeks? Months?
As MacPerl is rapidly becoming the data-conversion meta-tool, file-management language, and all-around Swiss Army chainsaw of choice for MacOS, you can't afford not to have this book.