Grasp Perl with Free Open-Source Books

The Perl Reference Guide

By Johan Vromans (31 pages)

The Perl Reference Guide is a concise book that examines Perl syntax, variables, literals, operators and precedence, statements, subroutines, packages and modules. Later chapters cover object oriented programming, functions (arithmetic, conversion, string, array and hash, search and replace), input/output, and more.

The author does not specify a specific license, but the book can be reproduced, printed and distributed freely for non-profit purposes.

CGI Programming on the World Wide Web

By Shishir Gundavaram (450 pages)

This book introduces the reader to a variety of applications that serve as models for CGI scripts. Complete applications in the book include an animated clock, a search tool, a survey, a quiz program, a game, a gateway to Usenet News, and an appointment calendar based on a clickable imagemap.

It includes forms, server side includes, hypermedia documents, multiple form interaction as well as advanced and creative CGI applications. It also teaches the reader how to debug and test CGI programs.

This book is out of print, but it has been made available online through the O’Reilly Open Books Project, with “open” copyright. There is a 2nd edition in paperback available to buy.

Learning Perl the Hard Way

By Allen B. Downey (69 pages)

Learning Perl the Hard Way is a book for people who already know how to program in another language, but have not previously developed in Perl. It tries to get through the basics as quickly as possible, and how to do fun things. It emphasizes good programming style in Perl.

Learning Perl the Hard Way has chapters on:

• Arrays and Scalars – describes the statements and operators needed to read command-line arguments, define and invoke subroutines, parse parameters, and read the contents of files
• Regular Expressions – covers pattern matching, anchors, quantifiers, alternation, capture sequences, minimal matching, extended patterns, operators, and subroutine semantics
• Hashes – with sections on stack operators, queue operators, hashes, frequency table, sort operator, checking whether an element is a member of a set, references to subroutines, hashes as parameters, markov generator, and generating random text
• Objects – goes through packages, the bless operator, methods, constructors, printing objects, and heaps
• Modules – examines variable-length codes, the frequency table, creating a new module, assembling the Huffman tree, inheritance, and more
• Callbacks and pipes

Learning Perl the Hard Way is a free book available under the GNU Free Documentation License.

Web Client Programming with Perl

By Clinton Wong (228 pages)

Web Client Programming with Perl shows you how to extend scripting skills to the Web. This book teaches you the basics of how browsers communicate with servers and how to write your own customized Web clients to automate common tasks. It is intended for those who are motivated to develop software that offers a more flexible and dynamic response than a standard Web browser.

A web client is an application that communicates with a web server, using Hypertext Transfer Protocol (HTTP).

This books helps developers learn how to:

• Automate repetitive queries on the Web
• Detect broken hyperlinks on your site
• Write simple “robots” that traverse hyperlinks across a site, and across the Web in general

Most of the examples in this book use Perl. The book does not teach Perl, but the techniques used in the book should be easily followed by anyone with some programming background and can be adapted to whatever language you choose.

The book is licensed under a Creative Commons license.

Programming Perl

By Kirrily Robert, Paul Fenwick, Jacinta Richardson (252 pages)

Programming Perl is a five day module in which you will learn how to program in Perl. It assumes you have programmed before, that you understand the concept of variables, conditional and looping constructs, and the use of user defined functions.

Chapters include:

• A brief guide to Perl and perldoc
• Creating and running a Perl program
• Perl variables
• Operators and functions
• Conditional constructs
• Subroutines
• Regular expressions
• Introduction to Modules
• External Files and Packages
• Writing modules
• Building modules with Module::Starter
• Testing your module
• Using Perl objects
• References and complex data structures
• Advanced regular expressions
• File I/O
• System interaction
• Practical exercises

This book is released under the Open Publications License 1.0.

Perl 5 Internals

By Simon Cozens (102 pages)

Perl 5 Internals is a three-hour course which provides a hands-on introduction to how the Perl interpreter works internally, how to go about testing and fixing bugs in the interpreter, and what the internals are likely to look like in the future of Perl, Perl 6.

The book covers:

• Development Structure
• Parts of the Interpreter
• Internal Variables
• The Lexer and the Parser
• Fundamental operations
• The Runtime Environment
• The Perl Compiler
• Hacking Perl
• Perl 6 Internals

This book is also released under the Open Publications License 1.0.

Picking up Perl

By Bradley M. Kuhn (66 pages)

Picking up Perl was primarily written to serve as a freely redistributable tutorial for the Perl language.

Topics covered include:

• Working with Scalars
• Arrays
• Control Structures
• Associative Arrays (Hashes)
• Regular Expressions
• Subroutines
• Background of Perl

This book is released under the terms of the GNU Free Documentation License, Version 1.1 or any later version.

Essential Perl

By Nick Parlante (25 pages)

We close with a short introduction to Perl. The book is targeted at developers with some programming knowledge.

Chapters include:

• What is Perl?
• Variables
• Strings
• Arrays
• Associative Arrays
• If, while, etc.
• File Input
• Print output
• Strings and Regular Expressions
• Subroutines
• Running External Programs

The author doesn’t specify a specific license, but says the document is free to be used, reproduced or sold as long as the copyright notice is maintained.