Perl Medic Transforming Legacy Code

Bring new power, performance, and scalability to your existing Perl code!

• Cure whatever ails your Perl code!
• Maintain, optimize, and scale any Perl software... whether you wrote it or not
• Perl software engineering best practices for enterprise environments
• Includes case studies and code in a fun-to-read format

Today's Perl developers spend 60-80% of their time working with existing Perl code. Now, there's a start-to-finish guide to understanding that code, maintaining it, updating it, and refactoring it for maximum performance and reliability. Peter J. Scott, lead author of Perl Debugged, has written the first systematic guide to Perl software engineering. Through extensive examples, he shows how to bring powerful discipline, consistency, and structure to any Perl program-new or old. You'll discover how to:

• Scale existing Perl code to serve larger network, Web, enterprise, or e-commerce applications
• Rewrite, restructure, and upgrade any Perl program for improved performance
• Bring standards and best practices to your entire library of Perl software
• Organize Perl code into modules and components that are easier to reuse
• Upgrade code written for earlier versions of Perl
• Write and execute better tests for your software...or anyone else's
• Use Perl in team-based, methodology-driven environments
• Document your Perl code more effectively and efficiently

If you've ever inherited Perl code that's hard to maintain, if you write Perl code others will read, if you want to write code that'll be easier for you to maintain, the book that comes to your rescue is Perl Medic.

If you code in Perl, you need to read this book.–Adam Turoff, Technical Editor, The Perl Review.

Perl Medic is more than a book. It is a well-crafted strategy for approaching, updating, and furthering the cause of inherited Perl programs.–Allen Wyke, co-author of several computer books including JavaScript Unleashed and Pure JavaScript.

Scott's explanations of complex material are smooth and deceptively simple. He knows his subject matter and his craft-he makes it look easy. Scott remains relentless practical-even the 'Analysis' chapter is filled with code and tests to run.–Dan Livingston, author of several computer books including Advanced Flash 5: Actionscript in Action

Peter J. Scott runs Pacific Systems Design Technologies, providing Perl training, application development, and enterprise systems analysis. He was a speaker on the 2002 Perl Whirl cruise and at YAPC::Canada, and he founded his local Perl Monger group. A software developer since 1981 and a Perl developer since 1992, he has also created programs for NASA's Jet Propulsion Laboratory. Scott graduated from Cambridge University, England, with a Master of Arts degree in Computer Science and now lives in the Pacific Northwest

PrefaceWorldwide, there are well over 200 billion lines of software that are fragmented, redundantly defined, hard to decipher, and highly inflexible... organizations run the risk of being mired down by a mountain of legacy code. William Ulrich, Legacy Systems: Transformation StrategiesCongratulations! Let's say you just graduated with a computer science degree and now, bucking the economic trend, you've landed a job at a prestigious company with a large information technology department. You're going to be replacing Bill, a programmer who won the lottery and was not seen or heard from again, save for a postcard from Puerto Vallarta two weeks later. Your coworkers warn you not to mention the postcard to your supervisor. You sit in Bill's cubicle throwing out pieces of vendor advertising left in the center desk drawer, thinking about how you're going to apply the elegant principles and sublime paradigms that professors inculcated in you at college. Just then, your supervisor arrives and, leaning over your shoulder, taps at your keyboard, bringing up a file."This is the last program Bill was working on. We think it's almost finished. We're behind schedule, so see if you can get it done by Thursday at the latest."As he leaves, you look at the program's tangle of misindented lines and cryptic variable names, searching for comments, but the only ones you can find read, "XXX-Must change" and "Kludge!-But should work." You wonder whether this is a corporate hazing ritual, but your instinct tells you otherwise.Welcome to the real world.In the real world, you're lucky if you get to spend all your time developing one new program after another. Much of the time you'll have to deal with someone else's. In the real world, programmers take over responsibility for programs written by people they might not know, like, or agree with. Even if you're fortunate enough to avoid this situation, you'll still have to maintain your own code; and one day you're going to look at something you wrote two years ago and ask, "What idiot wrote this?" Thereby arriving at more or less the same situation as the less fortunate programmers.This book is about taking over Perl code, whether written by someone else or by yourself at a time when you were less wise about maintainability. Many problems of code inheritance are common to all languages, but I have noticed them especially in Perl.Why does Perl tend to foster maintenance issues? The answer to this is the dark side of Perl's strength and motto: "There's More Than One Way To Do It" (enshrined in the acronym TMTOWTDI). Perl provides so many ways to do it that someone else quite possibly picked one that wasn't your way, or might have used several different ways all in the same program.The medical metaphor for this book stems from the rather drastic nature of the work we do as maintenance programmers. Often we must perform triage, deciding what code is worth saving and what is beyond redemption. Frequently we only have time for first aid, applying a field dressing to a ruptured program. We also have a hard time explaining our bills to the client. There may not be a Hippocratic Oath for programming, but it wouldn't hurt to come up with one.I wrote this book because I kept finding myself telling my students, "I'm going to teach you how to program Perl well, but I'd have to teach you a lot more before you could take over a program that wasn't written well, and you wouldn't appreciate taking that much time away from learning how to write good programs of your own." So I've written a book to fill that need.Perl is to computer languages as English is to human languages: bursting with irregular verbs, consistent only when it's convenient, borrowing terms from other languages to form a great melting pot of syntax. Most computer languages are described in terms of some kind of functional niche (Pascal: teachin