Perl Best Practices

Standards and Styles for Developing Maintainable Code

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Perl Best Practices

Standards and Styles for Developing Maintainable Code

By Damian Conway

Publisher: O'Reilly Media

Released: July 2005

Pages: 544

Many programmers code by instinct, relying on convenient habits or a "style" they picked up early on. They aren't conscious of all the choices they make, like how they format their source, the names they use for variables, or the kinds of loops they use. They're focused entirely on problems they're solving, solutions they're creating, and algorithms they're implementing. So they write code in the way that seems natural, that happens intuitively, and that feels good.

But if you're serious about your profession, intuition isn't enough. Perl Best Practices author Damian Conway explains that rules, conventions, standards, and practices not only help programmers communicate and coordinate with one another, they also provide a reliable framework for thinking about problems, and a common language for expressing solutions. This is especially critical in Perl, because the language is designed to offer many ways to accomplish the same task, and consequently it supports many incompatible dialects.

With a good dose of Aussie humor, Dr. Conway (familiar to many in the Perl community) offers 256 guidelines on the art of coding to help you write better Perl code--in fact, the best Perl code you possibly can. The guidelines cover code layout, naming conventions, choice of data and control structures, program decomposition, interface design and implementation, modularity, object orientation, error handling, testing, and debugging.

They're designed to work together to produce code that is clear, robust, efficient, maintainable, and concise, but Dr. Conway doesn't pretend that this is the one true universal and unequivocal set of best practices. Instead, Perl Best Practices offers coherent and widely applicable suggestions based on real-world experience of how code is actually written, rather than on someone's ivory-tower theories on howsoftware ought to be created.

Most of all, Perl Best Practices offers guidelines that actually work, and that many developers around the world are already using. Much like Perl itself, these guidelines are about helping you to get your job done, without getting in the way.

Praise for Perl Best Practices from Perl community members:

"As a manager of a large Perl project, I'd ensure that every member of my team has a copy of Perl Best Practices on their desk, and use it as the basis for an in-house style guide."-- Randal Schwartz

"There are no more excuses for writing bad Perl programs. All levels of Perl programmer will be more productive after reading this book."-- Peter Scott

"Perl Best Practices will be the next big important book in the evolution of Perl. The ideas and practices Damian lays down will help bring Perl out from under the embarrassing heading of "scripting languages". Many of us have known Perl is a real programming language, worthy of all the tasks normally delegated to Java and C++. With Perl Best Practices, Damian shows specifically how and why, so everyone else can see, too."-- Andy Lester

"Damian's done what many thought impossible: show how to build large, maintainable Perl applications, while still letting Perl be the powerful, expressive language that programmers have loved for years."-- Bill Odom

"Finally, a means to bring lasting order to the process and product of real Perl development teams."-- Andrew Sundstrom

"Perl Best Practices provides a valuable education in how to write robust, maintainable Perl, and is a definitive citation source when coaching other programmers."-- Bennett Todd

"I've been teaching Perl for years, and find the same question keeps being asked: Where can I find a reference for writing reusable, maintainable Perl code? Finally I have a decent answer."-- Paul Fenwick

"At last a well researched, well thought-out, comprehensive guide to Perl style. Instead of each of us developing our own, we can learn good practices from one of Perl's most prolific and experienced authors. I recommend this book to anyone who prefers getting on with the job rather than going back and fixing errors caused by syntax and poor style issues."-- Jacinta Richardson

"If you care about programming in any language read this book. Even if you don't intend to follow all of the practices, thinking through your style will improve it."-- Steven Lembark

"The Perl community's best author is back with another outstanding book. There has never been a comprehensive reference on high quality Perl coding and style until Perl Best Practices. This book fills a large gap in every Perl bookshelf."-- Uri Guttman

Chapter 1 Best Practices
1. Three Goals
2. This Book
3. Rehabiting
Chapter 2 Code Layout
1. Bracketing
2. Keywords
3. Subroutines and Variables
4. Builtins
5. Keys and Indices
6. Operators
7. Semicolons
8. Commas
9. Line Lengths
10. Indentation
11. Tabs
12. Blocks
13. Chunking
14. Elses
15. Vertical Alignment
16. Breaking Long Lines
17. Non-Terminal Expressions
18. Breaking by Precedence
19. Assignments
20. Ternaries
21. Lists
22. Automated Layout
Chapter 3 Naming Conventions
1. Identifiers
2. Booleans
3. Reference Variables
4. Arrays and Hashes
5. Underscores
6. Capitalization
7. Abbreviations
8. Ambiguous Abbreviations
9. Ambiguous Names
10. Utility Subroutines
Chapter 4 Values and Expressions
1. String Delimiters
2. Empty Strings
3. Single-Character Strings
4. Escaped Characters
5. Constants
6. Leading Zeros
7. Long Numbers
8. Multiline Strings
9. Here Documents
10. Heredoc Indentation
11. Heredoc Terminators
12. Heredoc Quoters
13. Barewords
14. Fat Commas
15. Thin Commas
16. Low-Precedence Operators
17. Lists
18. List Membership
Chapter 5 Variables
1. Lexical Variables
2. Package Variables
3. Localization
4. Initialization
5. Punctuation Variables
6. Localizing Punctuation Variables
7. Match Variables
8. Dollar-Underscore
9. Array Indices
10. Slicing
11. Slice Layout
12. Slice Factoring
Chapter 6 Control Structures
1. If Blocks
2. Postfix Selectors
3. Other Postfix Modifiers
4. Negative Control Statements
5. C-Style Loops
6. Unnecessary Subscripting
7. Necessary Subscripting
8. Iterator Variables
9. Non-Lexical Loop Iterators
10. List Generation
11. List Selections
12. List Transformation
13. Complex Mappings
14. List Processing Side Effects
15. Multipart Selections
16. Value Switches
17. Tabular Ternaries
18. do-while Loops
19. Linear Coding
20. Distributed Control
21. Redoing
22. Loop Labels
Chapter 7 Documentation
1. Types of Documentation
2. Boilerplates
3. Extended Boilerplates
4. Location
5. Contiguity
6. Position
7. Technical Documentation
8. Comments
9. Algorithmic Documentation
10. Elucidating Documentation
11. Defensive Documentation
12. Indicative Documentation
13. Discursive Documentation
14. Proofreading
Chapter 8 Built-in Functions
1. Sorting
2. Reversing Lists
3. Reversing Scalars
4. Fixed-Width Data
5. Separated Data
6. Variable-Width Data
7. String Evaluations
8. Automating Sorts
9. Substrings
10. Hash Values
11. Globbing
12. Sleeping
13. Mapping and Grepping
14. Utilities
Chapter 9 Subroutines
1. Call Syntax
2. Homonyms
3. Argument Lists
4. Named Arguments
5. Missing Arguments
6. Default Argument Values
7. Scalar Return Values
8. Contextual Return Values
9. Multi-Contextual Return Values
10. Prototypes
11. Implicit Returns
12. Returning Failure
Chapter 10 I/O
1. Filehandles
2. Indirect Filehandles
3. Localizing Filehandles
4. Opening Cleanly
5. Error Checking
6. Cleanup
7. Input Loops
8. Line-Based Input
9. Simple Slurping
10. Power Slurping
11. Standard Input
12. Printing to Filehandles
13. Simple Prompting
14. Interactivity
15. Power Prompting
16. Progress Indicators
17. Automatic Progress Indicators
18. Autoflushing
Chapter 11 References
1. Dereferencing
2. Braced References
3. Symbolic References
4. Cyclic References
Chapter 12 Regular Expressions
1. Extended Formatting
2. Line Boundaries
3. String Boundaries
4. End of String
5. Matching Anything
6. Lazy Flags
7. Brace Delimiters
8. Other Delimiters
9. Metacharacters
10. Named Characters
11. Properties
12. Whitespace
13. Unconstrained Repetitions
14. Capturing Parentheses
15. Captured Values
16. Capture Variables
17. Piecewise Matching
18. Tabular Regexes
19. Constructing Regexes
20. Canned Regexes
21. Alternations
22. Factoring Alternations
23. Backtracking
24. String Comparisons
Chapter 13 Error Handling
1. Exceptions
2. Builtin Failures
3. Contextual Failure
4. Systemic Failure
5. Recoverable Failure
6. Reporting Failure
7. Error Messages
8. Documenting Errors
9. OO Exceptions
10. Volatile Error Messages
11. Exception Hierarchies
12. Processing Exceptions
13. Exception Classes
14. Unpacking Exceptions
Chapter 14 Command-Line Processing
1. Command-Line Structure
2. Command-Line Conventions
3. Meta-options
4. In-situ Arguments
5. Command-Line Processing
6. Interface Consistency
7. Interapplication Consistency
Chapter 15 Objects
1. Using OO
2. Criteria
3. Pseudohashes
4. Restricted Hashes
5. Encapsulation
6. Constructors
7. Cloning
8. Destructors
9. Methods
10. Accessors
11. Lvalue Accessors
12. Indirect Objects
13. Class Interfaces
14. Operator Overloading
15. Coercions
Chapter 16 Class Hierarchies
1. Inheritance
2. Objects
3. Blessing Objects
4. Constructor Arguments
5. Base Class Initialization
6. Construction and Destruction
7. Automating Class Hierarchies
8. Attribute Demolition
9. Attribute Building
10. Coercions
11. Cumulative Methods
12. Autoloading
Chapter 17 Modules
1. Interfaces
2. Refactoring
3. Version Numbers
4. Version Requirements
5. Exporting
6. Declarative Exporting
7. Interface Variables
8. Creating Modules
9. The Standard Library
10. CPAN
Chapter 18 Testing and Debugging
1. Test Cases
2. Modular Testing
3. Test Suites
4. Failure
5. What to Test
6. Debugging and Testing
7. Strictures
8. Warnings
9. Correctness
10. Overriding Strictures
11. The Debugger
12. Manual Debugging
13. Semi-Automatic Debugging
Chapter 19 Miscellanea
1. Revision Control
2. Other Languages
3. Configuration Files
4. Formats
5. Ties
6. Cleverness
7. Encapsulated Cleverness
8. Benchmarking
9. Memory
10. Caching
11. Memoization
12. Caching for Optimization
13. Profiling
14. Enbugging

Appendix Essential Perl Best Practices
Appendix Perl Best Practices
1. , Code Layout
2. , Naming Conventions
3. , Values and Expressions
4. , Variables
5. , Control Structures
6. , Documentation
7. , Built-in Functions
8. , Subroutines
9. , I/O
10. , References
11. , Regular Expressions
12. , Error Handling
13. , Command-Line Processing
14. , Objects
15. , Class Hierarchies
16. , Modules
17. , Testing and Debugging
18. , Miscellanea
Appendix Editor Configurations
1. vim
2. vile
3. Emacs
4. BBEdit
5. TextWrangler
Appendix Recommended Modules and Utilities
1. Recommended Core Modules
2. Recommended CPAN Modules
3. Utility Subroutines
Appendix Bibliography
1. Perl Coding and Development Practices
2. General Coding and Development Practices
Colophon

Title:

Perl Best Practices

By:

Damian Conway

Publisher:

O'Reilly Media

Formats:

Print
Ebook
Safari Books Online

Print:

July 2005

Ebook:

June 2009

Pages:

544

Print ISBN:

978-0-596-00173-5

| ISBN 10:

0-596-00173-8

Ebook ISBN:

978-0-596-15900-9

| ISBN 10:

0-596-15900-5

Damian Conway

Damian Conway holds a PhD in Computer Science and is an honorary Associate Professor with the School of Computer Science and Software Engineering at Monash University, Melbourne, Australia.

Currently he runs an international IT training company--Thoughtstream--which provides programmer development from beginner to masterclass level throughout Europe, North America, and Australasia.

Damian was the winner of the 1998, 1999, and 2000 Larry Wall Awards for Practical Utility. The best technical paper at the annual Perl Conference was subsequently named in his honour. He is a member of the technical committee for The Perl Conference, a keynote speaker at many Open Source conferences, a former columnist for The Perl Journal, and author of the book Object Oriented Perl. In 2001 Damian received the first "Perl Foundation Development Grant" and spent 20 months working on projects for the betterment of Perl.

A popular speaker and trainer, he is also the author of numerous well-known Perl modules, including Parse::RecDescent (a sophisticated parsing tool), Class::Contract (design-by-contract programming in Perl), Lingua::EN::Inflect (rule-based English transformations for text generation), Class::Multimethods (multiple dispatch polymorphism), Text::Autoformat (intelligent automatic reformatting of plaintext), Switch (Perl's missing case statement), NEXT (resumptive method dispatch), Filter::Simple (Perl-based source code manipulation), Quantum::Superpositions (auto-parallelization of serial code using a quantum mechanical metaphor), and Lingua::Romana::Perligata (programming in Latin).

Most of his time is now spent working with Larry Wall on the design of the new Perl 6 programming language.

View Damian Conway's full profile page.

Description

Table of Contents

Product Details

About the Author

Recommended for You

Chapter 1 Best Practices

Three Goals

This Book

Rehabiting

Chapter 2 Code Layout

Bracketing

Keywords

Subroutines and Variables

Builtins

Keys and Indices

Operators

Semicolons

Commas

Line Lengths

Indentation

Tabs

Blocks

Chunking

Elses

Vertical Alignment

Breaking Long Lines

Non-Terminal Expressions

Breaking by Precedence

Assignments

Ternaries

Lists

Automated Layout

Chapter 3 Naming Conventions

Identifiers

Booleans

Reference Variables

Arrays and Hashes

Underscores

Capitalization

Abbreviations

Ambiguous Abbreviations

Ambiguous Names

Utility Subroutines

Chapter 4 Values and Expressions

String Delimiters

Empty Strings

Single-Character Strings

Escaped Characters

Constants

Leading Zeros

Long Numbers

Multiline Strings

Here Documents

Heredoc Indentation

Heredoc Terminators

Heredoc Quoters

Barewords

Fat Commas

Thin Commas

Low-Precedence Operators

Lists

List Membership

Chapter 5 Variables

Lexical Variables

Package Variables

Localization

Initialization

Punctuation Variables

Localizing Punctuation Variables

Match Variables

Dollar-Underscore

Array Indices

Slicing

Slice Layout

Slice Factoring

Chapter 6 Control Structures

If Blocks

Postfix Selectors

Other Postfix Modifiers

Negative Control Statements

C-Style Loops

Unnecessary Subscripting

Necessary Subscripting

Iterator Variables

Non-Lexical Loop Iterators