Intermediate Perl

Perl programmers need a clear roadmap for improving their skills. Intermediate Perl teaches a working knowledge of Perl's objects, references, and modules - all of which makes the language so versatile and effective. Written by the authors of the bestselling Llama book, Learning Perl, this guide offers a controlled introduction to intermediate programming in Perl. Topics include packages and namespaces, references and scoping, manipulating complex data structures, writing and using modules, package implementation, and using CPAN. Intermediate Perl follows the successful format of O'Reilly Learning books: each chapter is small enough to be read in just an hour or two and ends with a series of exercises to help the reader practice each new skill. This book will take Perl programmers to the next level.

Randal L. Schwartz is a renowned expert on the Perl programming language. In addition to writing "Learning Perl" and the first two editions of "Programming Perl", he has been the Perl columnist for UNIX Review, Web Techniques, Sys Admin, and Linux Magazine. He has contributed to a dozen Perl books, and over 200 magazine articles. Randal runs a Perl training and consulting company (Stonehenge Consulting Services), and is highly sought-after as a speaker for his combination of technical skill, comedic timing, and crowd rapport. He's also a pretty good Karaoke singer.

brian d foy has been an instructor for Stonehenge Consulting Services since 1998. He founded the first Perl user group, the New York Perl Mongers, as well as the Perl advocacy nonprofit Perl Mongers, Inc., which helped form more than 200 Perl user groups across the globe. He maintains the perlfaq portions of the core Perl documentation, several modules on CPAN, and some stand-alone scripts. He's the publisher of The Perl Review and is a frequent speaker at conferences. His writings on Perl appear on The O'Reilly Network and use.perl.org, and in The Perl Journal, Dr. Dobbs Journal, and The Perl Review.

Tom Phoenix has been working in the field of education since 1982. After more than thirteen years of dissections, explosions, work with interesting animals, and high-voltage sparks during his work at a science museum, he started teaching Perl classes for Stonehenge Consulting Services, where he's worked since 1996. Since then, he has traveled to many interesting locations, so you might see him soon at a Perl Mongers' meeting. When he has time, he answers questions on Usenet's comp.lang.perl.misc and comp.lang.perl.moderated newsgroups, and contributes to the development and usefulness of Perl. Besides his work with Perl, Perl hackers, and related topics, Tom spends his time on amateur cryptography and speaking Esperanto. His home is in Portland, Oregon.

Foreword

xi

Preface

xiii

1. Introduction

1

(3)

What Should You Know Already?

2

(1)

What About All Those Footnotes?

2

(1)

What's with the Exercises?

2

(1)

What If I'm a Perl Course Instructor?

3

(1)

2. Intermediate Foundations

4

(7)

List Operators

4

(4)

Trapping Errors with eval

8

(1)

Dynamic Code with eval

9

(1)

Exercises

10

(1)

3. Using Modules

11

(10)

The Standard Distribution

11

(1)

Using Modules

12

(1)

Functional Interfaces

12

(1)

Selecting What to Import

13

(1)

Object-Oriented Interfaces

14

(1)

A More Typical Object-Oriented Module: Math::BigInt

15

(1)

The Comprehensive Perl Archive Network

15

(1)

Installing Modules from CPAN

16

(1)

Setting the Path at the Right Time

17

(2)

Exercises

19

(2)

4. Introduction to References

21

(13)

Performing the Same Task on Many Arrays

21

(2)

Taking a Reference to an Array

23

(1)

Dereferencing the Array Reference

24

(2)

Getting Our Braces Off

26

(1)

Modifying the Array

26

(1)

Nested Data Structures

27

(2)

Simplifying Nested Element References with Arrows

29

(1)

References to Hashes

30

(2)

Exercises

32

(2)

5. References and Scoping

34

(16)

More Than One Reference to Data

34

(1)

What If That Was the Name?

35

(1)

Reference Counting and Nested Data Structures

36

(2)

When Reference Counting Goes Bad

38

(2)

Creating an Anonymous Array Directly

40

(2)

Creating an Anonymous Hash

42

(2)

Autovivification

44

(3)

Autovivification and Hashes

47

(1)

Exercises

48

(2)

6. Manipulating Complex Data Structures

50

(13)

Using the Debugger to View Complex Data

50

(4)

Viewing Complex Data with Data::Dumper

54

(2)

YAML

56

(1)

Storing Complex Data with Storable

57

(2)

Using the map and grep Operators

59

(1)

Applying a Bit of Indirection

59

(1)

Selecting and Altering Complex Data

60

(2)

Exercises

62

(1)

7. Subroutine References

63

(16)

Referencing a Named Subroutine

63

(5)

Anonymous Subroutines

68

(2)

Callbacks

70

(1)

Closures

70

(2)

Returning a Subroutine from a Subroutine

72

(3)

Closure Variables as Inputs

75

(1)

Closure Variables as Static Local Variables

75

(2)

Exercise

77

(2)

8. Filehandle References

79

(10)

The Old Way

79

(1)

The Improved Way

80

(1)

The Even Better Way

81

(1)

IO::Handle

82

(4)

Directory Handle References

86

(1)

Exercises

87

(2)

9. Practical Reference Tricks

89

(12)

Review of Sorting

89

(2)

Sorting with Indices

91

(1)

Sorting Efficiently

92

(1)

The Schwartzian Transform

93

(1)

Multi-Level Sort with the Schwartzian Transform

94

(1)

Recursively Defined Data

95

(1)

Building Recursively Defined Data

96

(2)

Displaying Recursively Defined Data

98

(1)

Exercises

99

(2)

10. Building Larger Programs

101

(14)

The Cure for the Common Code

101

(1)

Inserting Code with eval

102

(1)

Using do

103

(2)

Using require

105

(1)

require and @INC

106

(3)

The Problem of Namespace Collisions

109

(1)

Packages as Namespace Separators

110

(2)

Scope of a Package Directive

112

(1)

Packages and Lexicals

113

(1)

Exercises

113

(2)

11. Introduction to Objects

115

(11)

If We Could Talk to the Animals...

115

(2)

Introducing the Method Invocation Arrow

117

(1)

The Extra Parameter of Method Invocation

118

(1)

Calling a Second Method to Simplify Things

119

(1)

A Few Notes About @ISA

120

(1)

Overriding the Methods

121

(2)

Starting the Search from a Different Place

123

(1)

The SUPER Way of Doing Things

124

(1)

What to Do with @_

124

(1)

Where We Are So Far...

124

(1)

Exercises

125

(1)

12. Objects with Data

126

(13)

A Horse Is a Horse, of Course of Course—or Is It?

126

(1)

Invoking an Instance Method

127

(1)

Accessing the Instance Data

128

(1)

How to Build a Horse

128

(1)

Inheriting the Constructor

129

(1)

Making a Method Work with Either Classes or Instances

130

(1)

Adding Parameters to a Method

131

(1)

More Interesting Instances

132

(1)

A Horse of a Different Color

133

(1)

Getting Our Deposit Back

133

(2)

Don't Look Inside the Box

135

(1)

Faster Getters and Setters

136

(1)

Getters That Double as Setters

136

(1)

Restricting a Method to Class-Only or Instance-Only

137

(1)

Exercise

137

(2)

13. Object Destruction

139

(15)

Cleaning Up After Yourself

139

(2)

Nested Object Destruction

141

(3)

Beating a Dead Horse

144

(1)

Indirect Object Notation

145

(2)

Additional Instance Variables in Subclasses

147

(2)

Using Class Variables

149

(1)

Weakening the Argument

150

(2)

Exercise

152

(2)

14. Some Advanced Object Topics

154

(8)

UNIVERSAL Methods

154

(1)

Testing Our Objects for Good Behavior

155

(1)

AUTOLOAD as a Last Resort

156

(1)

Using AUTOLOAD for Accessors

157

(1)

Creating Getters and Setters More Easily

158

(2)

Multiple Inheritance

160

(1)

Exercises

161

(1)

15. Exporter

162

(9)

What use Is Doing

162

(1)

Importing with Exporter

163

(1)

@EXPORT and @EXPORT_OK

164

(1)

%EXPORT_TAGS

165

(1)

Exporting in a Primarily 00 Module

166

(2)

Custom Import Routines

168

(1)

Exercises

169

(2)

16. Writing a Distribution

171

(18)

There's More Than One Way To Do It

172

(1)

Using h2xs

173

(6)

Embedded Documentation

179

(4)

Controlling the Distribution with Makefile.PL

183

(1)

Alternate Installation Locations (PREFIX=...)

184

(1)

Trivial make test

185

(1)

Trivial make install

186

(1)

Trivial make dist

186

(1)

Using the Alternate Library Location

187

(1)

Exercise

188

(1)

17. Essential Testing

189

(14)

More Tests Mean Better Code

189

(1)

A Simple Test Script

190

(1)

The Art of Testing

191

(2)

The Test Harness

193

(2)

Writing Tests with Test::More

195

(2)

Testing Object-Oriented Features

197

(2)

A Testing To-Do List

199

(1)

Skipping Tests

200

(1)

More Complex Tests (Multiple Test Scripts)

201

(1)

Exercise

201

(2)

18. Advanced Testing

203

(13)

Testing Large Strings

203

(1)

Testing Files

204

(1)

Testing STDOUT or STDERR

205

(3)

Using Mock Objects

208

(1)

Testing POD

209

(1)

Coverage Testing

210

(1)

Writing Your Own Test::* Modules

211

(3)

Exercises

214

(2)

19. Contributing to CPAN

216

(5)

The Comprehensive Perl Archive Network

216

(1)

Getting Prepared

216

(1)

Preparing Your Distribution

217

(1)

Uploading Your Distribution

218

(1)

Announcing the Module

219

(1)

Testing on Multiple Platforms

219

(1)

Consider Writing an Article or Giving a Talk

220

(1)

Exercise

220

(1)

Appendix: Answers to Exercises

221

(28)

Index

249

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Summary

Author Biography

Table of Contents

Supplemental Materials