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Mastering Perl by brian d foy

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Chapter 1. Introduction: Becoming a Master

This book isn’t going to make you a Perl master; you have to do that for yourself by programming a lot of Perl, trying a lot of new things, and making a lot of mistakes. I’m going to help you get on the right path. The road to mastery is one of self-reliance and independence. As a Perl master, you’ll be able to answer your own questions as well as those of others.

In the golden age of guilds, craftsmen followed a certain path, both literally and figuratively, as they mastered their craft. They started as apprentices and would do the boring bits of work until they had enough skill to become the more trusted journeymen. The journeyman had greater responsibility but still worked under a recognized master. When he had learned enough of the craft, the journeyman would produce a “master work” to prove his skill. If other masters deemed it adequately masterful, the journeyman became a recognized master himself.

The journeymen and masters also traveled (although people disagree on whether that’s where the “journey” part of the name came from) to other masters, where they would learn new techniques and skills. Each master knew things the others didn’t, perhaps deliberately guarding secret methods, or knew it in a different way. Part of a journeyman’s education was learning from more than one master.

Interactions with other masters and journeymen continued the master’s education. He learned from those masters with more experience and learned from himself as he taught journeymen, who also taught him because they brought skills they learned from other masters.

The path an apprentice followed affected what he learned. An apprentice who studied with more masters was exposed to many more perspectives and ways of teaching, all of which he could roll into his own way of doing things. Odd teachings from one master could be exposed by another, giving the apprentice a balanced view on things. Additionally, although the apprentice might be studying to be a carpenter or a mason, different masters applied those skills to different goals, giving the apprentice a chance to learn different applications and ways of doing things.

Unfortunately, we don’t operate under the guild system. Most Perl programmers learn Perl on their own (I’m sad to say, as a Perl instructor), program on their own, and never get the advantage of a mentor. That’s how I started. I bought the first edition of Learning Perl and worked through it on my own. I was the only person I knew who knew what Perl was, although I’d seen it around a couple of times. Most people used what others had left behind. Soon after that, I discovered comp.lang.perl.misc and started answering any question that I could. It was like self-assigned homework. My skills improved and I got almost instantaneous feedback, good and bad, and I learned even more Perl. I ended up with a job that allowed me to program Perl all day, but I was the only person in the company doing that. I kept up my homework on comp.lang.perl.misc.

I eventually caught the eye of Randal Schwartz, who took me under his wing and started my Perl apprenticeship. He invited me to become a Perl instructor with Stonehenge Consulting Services, and then my real Perl education began. Teaching, meaning figuring out what you know and how to explain it to others, is the best way to learn a subject. After a while of doing that, I started writing about Perl, which is close to teaching, although with correct grammar (mostly) and an editor to correct mistakes.

That presents a problem for Mastering Perl, which I designed to be the third book of a trilogy starting with Learning Perl and Intermediate Perl, both of which I’ve had a hand in. Each of those are about 300 pages, and that’s what I’m limited to here. How do I encapsulate the years of my experience in such a slim book?

In short, I can’t. I’ll teach you what I think you should know, but you’ll also have to learn from other sources. As with the old masters, you can’t just listen to one person. You need to find other masters, too, and that’s also the great thing about Perl: you can do things in so many different ways. Some of these masters have written very good books, from this publisher and others, so I’m not going to duplicate those topics here, as I discuss in a moment.

What It Means to Be a Master

This book takes a different tone from Learning Perl and Intermediate Perl, which we designed as tutorial books. Those mostly cover the details of the Perl language and only a little on the practice of programming. Mastering Perl, however, puts more responsibility on you, the reader.

Now that you’ve made it this far in Perl, you’re working on your ability to answer your own questions and figure out things on your own, even if that’s a bit more work than simply asking someone. The very act of doing it yourself builds your experience as well as not annoying your coworkers.

Although I don’t cover other languages in this book, like Advanced Perl Programming, First Edition, by Sriram Srinivasan (O’Reilly) and Mastering Regular Expressions by Jeffrey Friedl (O’Reilly) do, you should learn some other languages. This informs your Perl knowledge and gives you new perspectives, some that make you appreciate Perl more and others that help you understand its limitations.

And, as a master, you will run into Perl’s limitations. I like to say that if you don’t have a list of five things you hate about Perl and the facts to back them up, you probably haven’t done enough Perl. It’s not really Perl’s fault. You’ll get that with any language. The mastery comes in by knowing these things and still choosing Perl because its strengths outweigh the weakness for your application. You’re a master because you know both sides of the problem and can make an informed choice that you can explain to others.

All of that means that becoming a master involves work, reading, and talking to other people. The more you do, the more you learn. There’s no shortcut to mastery. You may be able to learn the syntax quickly, as in any other language, but that will be the tiniest portion of your experience. Now that you know most of Perl, you’ll probably spend your time reading some of the “meta”-programming books that discuss the practice of programming rather than just slinging syntax. Those books will probably use a language that’s not Perl, but I’ve already said you need to learn some other languages, if only to be able to read these books. As a master, you’re always learning.

Becoming a master involves understanding more than you need to, doing quite a bit of work on your own, and learning as much as you can from the experience of others. It’s not just about the code you write, because you have to deal with the code from many other authors too.

It may sound difficult, but that’s how you become a master. It’s worth it, so don’t give up. Good luck!

Who Should Read This Book

I wrote this book as a successor to Intermediate Perl, which covered the basics of references, objects, and modules. I’ll assume that you already know and feel comfortable with those features. Where possible, I make references to Intermediate Perl in case you need to refresh your skills on a topic.

If you’re coming directly from another language and haven’t used Perl yet, or have only used it lightly, you might want to skim Learning Perl and Intermediate Perl to get the basics of the language. Still, you might not recognize some of the idioms that come with experience and practice. I don’t want to tell you not to buy this book (hey, I need to pay my mortgage!), but you might not get the full value I intend, at least not right away.

How to Read This Book

I’m not writing a third volume of “Yet More Perl Features.” I want to teach you how to learn Perl on your own. I’m setting you on your own path to mastery, and as an apprentice, you’ll need to do some work on your own. Sometimes this means I’ll show you where in the Perl documentation to get the answers (meaning I can use the saved space to talk about other topics).

What Should You Know Already?

I’ll presume that you already know everything that we covered in Learning Perl and Intermediate Perl. By we, I mean the Stonehenge Consulting Services crew and bestselling Perl coauthors Randal Schwartz, Tom Phoenix, and me.

Most importantly, you should know these subjects, each of which implies knowledge of other subjects:

  • Using Perl modules

  • Writing Perl modules

  • References to variables, subroutines, and filehandles

  • Basic regular expression syntax and workings

  • Object-oriented Perl

If I want to discuss something not in either of those books, I’ll explain it in a bit more depth. Even if we did cover it in the previous books, I might cover it again just because it’s that important.

What I Cover

After learning the basic syntax of Perl in Learning Perl and the basics of modules and team programming in Intermediate Perl, the next thing you need to learn are the idioms of Perl and the integration of the skills that you already have to create robust and scalable applications that other people can use without your help.

I’ll cover some subjects you’ve seen in those two books, but in more depth. As we said in Learning Perl, we sometimes told white lies to simplify the details and to get you going as soon as possible without getting bogged down. Now it’s time to get a bit dirty in the bogs.

Don’t mistake my coverage of a subject for an endorsement, though. There are millions of Perl programmers in the world, and each has her own way of doing things. Part of becoming a Perl master involves reading quite a bit of Perl even if you wouldn’t write that Perl yourself. I’ll endeavor to tell you when I think you shouldn’t do something, but that’s really just my opinion. As you strive to be a good programmer, you’ll need to know more than you’ll use. Sometimes I’ll show things I don’t want you to use, but I know you’ll see in code from other people. Oh well, it’s not a perfect world.

Not all programming is about adding or adjusting features in code. Sometimes it’s pulling code apart to inspect it and watch it do its magic. Other times it’s about getting rid of code that you don’t need. The practice of programming is more than creating applications. It’s also about managing and wrangling code. Some of the techniques I’ll show are for analysis, not your own development.

What I Don’t Cover

As I talked over the idea of this book with the editors, we decided not to duplicate the subjects more than adequately covered by other books. You need to learn from other masters, too, and I don’t really want to take up more space on your shelf than I really need. Ignoring those subjects gives me the double bonus of not writing those chapters and using that space for other things. You should already have read those other books anyway.

That doesn’t mean that you get to ignore those subjects, though, and where appropriate I’ll point you to the right book. In Appendix A, I list some books I think you should add to your library as you move towards Perl mastery. Those books are by other Perl masters, each of whom has something to teach you. At the end of most chapters I point you toward other resources as well. A master never stops learning.

Since you’re already here, though, I’ll just give you the list of topics I’m explicitly avoiding, for whatever reason: Perl internals, embedding Perl, threads, best practices, object-oriented programming, source filters, and dolphins. This is a dolphin-safe book.

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