Perl Tutorials - Herong's Tutorial Examples

By Herong Yang

This Perl tutorial book is a collection of notes and sample codes written by the author while he was learning Perl language himself. Topics include introduction of ActivePerl; data types, variables and expressions; scalars, arrays, hash maps, and references; input/output and file systems; DBM files and MySQL access; socket communication; generating executables; XML::Simple and RPC:XML modules; LWP::UserAgent, HTTP::Request and SOAP::Lite modules; CGI, and IIS/Apache integrations. Updated in 2024 (Version v6.02) with minor updates.

For latest updates and free sample chapters, visit https://www.herongyang.com/Perl.

• Language: English
• Publisher: Lulu.com
• Release date: Mar 2, 2020
• ISBN: 9781678187040

Book preview

The Front Cover

Perl Tutorials

- Herong's Tutorial Examples

Icon

v6.02, 2024

Herong Yang

© 1995-2024 Herong Yang. All rights reserved.

ISBN: 978-1-6781-8704-0

This Perl tutorial book is a collection of notes and sample codes written by the author while he was learning Perl language himself. Topics include introduction of ActivePerl; data types, variables and expressions; scalars, arrays, hash maps, and references; input/output and file systems; DBM files and MySQL access; socket communication; generating executables; XML::Simple and RPC:XML modules; LWP::UserAgent, HTTP::Request and SOAP::Lite modules; CGI, and IIS/Apache integrations. Updated in 2024 (Version v6.02) with minor updates.

Table of Contents

About This Book

Perl on Linux Systems

Perl Installation on Linux Systems

Running Perl Scripts on Linux Systems

ActivePerl on Windows Systems

What Is ActivePerl?

Install ActivePerl on Windows Systems

Running Perl Scripts on Windows Systems

Data Types: Values and Variables

Scalar Values and List Values

Scalar Value Constructors

Scalar Value Interpretation

List Value Constructors

Variables - Scalar, Array and Hash

Using Scalar Variables

Using Array Variables

Using Hash Variables

undef Value and Undefined Variables

Expressions, Operations and Simple Statements

What Is an Expression?

Expression Evaluation Context

Simple Statements and Modifiers

User Defined Subroutines

Declaring and Calling Subroutines

SubParamList.pl - Example on Parameter List

SubParamAlias.pl - Example on Parameters as Alias

SubReturnValue.pl - Example on Return Values

SubCalling.pl - Example on Calling Formats

Perl Built-in Debugger

Commonly Used Debugging Commands

Debugging Tutorial Session

Name Spaces and Perl Module Files

Including Script Codes from Other Files

do() Function - Including Script Files

require() Function - Including Script Files

package Statement - Switching Name Space

BEGIN(), CHECK(), INIT() and END() Functions

Defining Your Own Perl Module

CalendarModule.pm - A Sample Perl Module

Symbolic (or Soft) References

Using Symbolic References

$$name - Replacing Identifiers by Scalar Variables

${EXPR} - Replacing Identifiers by Expressions

EXPR->* - The Dereference Operator

$$$name - Nested Symbolic References

Hard References - Addresses of Memory Objects

\* - Creating Hard References

Using Hard References

$$name - Replacing Identifiers by Scalar Variables

${EXPR} - Replacing Identifiers by Expressions

EXPR->* - The Dereference Operator

$$$name - Nested Hard References

\$b-\$a - Using Hard References in Other Operations

Objects (or References) and Classes (or Packages)

Basic Concepts of Classes and Objects

Invoking Package Subroutines as Class Methods

bless() - Converting References to Objects

Invoking Package Subroutines as Object Methods

Class Variables and Object Variables

new() Method - Creating Objects by the Class

CalendarClass.pm - A Perl Class Example

Typeglob and Importing Identifiers from Other Packages

Typeglob, Symbolic Table and Identifier Aliases

Accessing Identifiers from Other Packages as Aliases

Exporting and Importing Package Identifiers

String Built-in Functions and Performance

String Related Built-in Functions

Performance of Perl substr() and index()

Performance of Java substring() and indexOf()

File Handles and Data Input/Output

open() - Opening File Handles for Input and Output

print() - Printing Output to File Handles

- Reading Data from File Handles

Open Files in Binary Mode

binmode() - Opening Files for Binary Input

binmode() - Opening Files for Binary Output

Copy.pl - Copying Binary Files

Bin2Hex.pl - Converting Binary Data to Hex Numbers

Open Directories and Read File Names

opendir() - Open Directory to Read File Names

opendir.pl - Sample Program to Read Directories

DirTree.pl - Displaying the Directory Tree

DirGrep.pl - Searching Text in Directory Files

File System Functions and Operations

Built-in Functions to Work with the File System

File Test Operators

stat() - Returns File Statistics

Image and Picture Processing

Imager - Create and Save Image

Imager - Draw Graphical Elements

Imager - Convert Image File Format

Imager::File::PNG - PNG File Format

Install LIBPNG from Source Code

Install Imager::File::PNG Manually

Install PerlMagick from Source Code

Using DBM Database Files

dbmopen() - Opening DBM Files with Hash Variables

DBM Database Example - English French Dictionary

DBM Database Example - Book Records with Multiple Fields

Using MySQL Database Server

Installing Database Module for MySQL

HelloMySQL.pl - My First Perl Program with MySQL

Socket Communication Over the Internet

What Is Socket Communication?

connect() - Establishing a Socket Communication

ReverseEchoer.pl - A Simple Socket Server Program

SocketClient.pl - A Simple Socket Client Program

gethostbyaddr() - Network Utility Functions

Socket.pm - The Socket Module

XML::Simple Module - XML Parser and Generator

XMLin() and XMLout() Methods

XML Parsing Options

forcearray - Forcing Element Contents as Arrays

suppressempty - Parsing Empty Elements

keyattr - Namings Attributes as Keys

XmlSimpleHash.pl - XML Hash Example

XML Communication Model

XML Messages over Socket Connections

GameServer.pl - XML Communication Server Example

GameClient.pl - XML Communication Client Example

SOAP::Lite - SOAP Server-Client Communication Module

What Is SOAP?

What Is SOAP::Lite?

SOAP::Transport::TCP - SOAP Server with TCP Protocol

SoapTcpClient.pl - SOAP Client Example with TCP Protocol

SOAP::Lite Tracing Functions

SOAP::Transport::HTTP - SOAP Server with HTTP Protocol

Perl Programs as IIS Server CGI Scripts

Configuring IIS 5.0 for Perl Programs

perl.exe vs. perlis.dll

CGI (Common Gateway Interface)

What Is Common Gateway Interface (CGI)?

IIS Environment Variables

QUERY_STRING - CGI Query String

Calculator.pl - CGI Application Example

XML-RPC - Remote Procedure Call with XML and HTTP

What Is XML-RPC?

Defining a Remote Method Call in XML

Sending a Remote Method Call as a HTTP Request

Defining Returning Values of a Remote Method Call

Receiving Returning Values as a HTTP Response

RPC::XML - Perl Implementation of XML-RPC

What Is RPC::XML?

RPC::XML::Server - XML-RPC Server Interface Class

RPC::XML Client and Data Classes

Installing NMake 1.5

Installing RPC::XML Module

RpcXmlServer.pl - RPC::XML Server Sample Program

RpcXmlClient.pl - RPC::XML Client Sample Program

Sending Arrays with Remote Method Calls

Integrating Perl with Apache Web Server

Downloading Apache HTTP Server 2.2.25 for Windows

Installing Apache HTTP Server 2.2.25 on Windows

Publishing HTML Documents as Web Pages

Starting and Stopping Apache Server

Running Perl Scripts in cgi-bin

printenv.pl - Testing Perl CGI Environment

500 Internal Server Error

cgi-lib.pl - The Standard Library for CGI Scripts

ReadParse() - Parsing Web Form Input Values

Running Perl Scripts in htdocs

CGI.pm Module for Building Web Pages

What Is CGI.pm?

Generating HTML Document with CGI.pm

Retrieving Query Parameters and Headers

Retrieving Environment and Script Information

Redirecting Browser to a URI

Refresh http-equiv Meta Tag

What Is CGI::Cookie?

Retrieving and Setting HTTP Cookies

LWP::UserAgent and Web Site Testing

What Is LWP::UserAgent?

What Is HTTP::Response?

What Is HTTP::Request?

LWP-UserAgent-GET.pl - Sending a GET Request

LWP-UserAgent-GET-Redirect.pl - Following HTTP Redirects

http-equiv=Refresh Meta Tag not Followed

LWP-UserAgent-POST.pl - Posting Form Data

post() Method not Following Redirect Location

LWP-UserAgent-POST-Redirect.pl - Posting with Redirects

What Is HTTP::Cookies?

LWP-UserAgent-Request.pl - GET, POST and Cookies

LWP-UserAgent-Request.pl - Login to facebook.com

HTTP::Cookies save() not Saving Temporary Cookies

LWP-UserAgent-Request-Cookies.pl - Sending Request with Cookies

Converting Perl Script to Executable Binary

Perl Script Conversion Tools

Installing Perl Dev Kit (PDK)

Running PerlApp to Convert *.pl to *.exe

Managing Perl Engine and Modules on macOS

Perl Version Pre-Installed on macOS

Install Xcode Command Line Tools

Configure CPAN Shell

Install Perl Module from CPAN

Install Perl Module from Source Code

Archived Tutorials

Archived: Install ActivePerl v5.18.1 on Windows Systems

Archived: Install ActivePerl v5.8.8 on Windows Systems

References

Keywords: Perl, Script, Language, Tutorial, Example

Perl Tutorials - Herong's Tutorial Examples

∟ About This Book

This section provides some detailed information about this book - Perl Tutorials - Herong's Tutorial Examples.

Title: Perl Tutorials - Herong's Tutorial Examples

Author: Herong Yang - Contact by email via [e-mail].

Category: Perl/Tutorial

Version/Edition: v6.02, 2024

Number of pages in PDF format: 333

Description: This Perl tutorial book is a collection of notes and sample codes written by the author while he was learning Perl language himself. Topics include introduction of ActivePerl; data types, variables and expressions; scalars, arrays, hash maps, and references; input/output and file systems; DBM files and MySQL access; socket communication; generating executables; XML::Simple and RPC:XML modules; LWP::UserAgent, HTTP::Request and SOAP::Lite modules; CGI, and IIS/Apache integrations. Updated in 2024 (Version v6.02) with minor updates.

Keywords: Perl, Script, Language, Example, Code, Tutorial, Book.

Copyright:

This book is under © 1995-2024 Herong Yang. All rights reserved.

Material in this book may not be published, broadcasted, rewritten or redistributed in any form.

The example codes is provided as-is, with no warranty of any kind.

Revision history:

Version v6.02, 2024. Minor updates.

Version v6.00, 2020. Added tutorials for macOS and Linux.

Version v5.50, 2019. Updated with Perl v5.26.1.

Version v5.30, 2014. Added tutorials on CGI.pm and LWP::UserAgent.

Version v5.00, 2005. Added tutorials on XML-RPC.

Version v4.00, 2002. Added tutorials on SOAP.

Version v3.00, 1999. Added tutorials on classes.

Version v2.00, 1996. Added tutorials on DBM files.

Version v1.00, 1995. First edition.

Web version: https://www.herongyang.com/Perl - Provides free sample chapters, latest updates and readers' comments. The Web version of this book has been viewed a total of:

2,143,629 times as of December 2023.

2,090,689 times as of December 2022.

1,969,004 times as of December 2021.

1,836,525 times as of December 2020.

1,730,429 times as of December 2019.

1,642,156 times as of December 2018.

1,547,354 times as of December 2017.

1,433,821 times as of December 2016.

1,307,643 times as of December 2015.

1,162,501 times as of December 2014.

979,141 times as of December 2013.

813,834 times as of December 2012.

650,091 times as of December 2011.

490,036 times as of December 2010.

356,604 times as of December 2009.

207,629 times as of December 2008.

137,317 times as of December 2007.

92,461 times as of December 2006.

PDF/EPUB version: https://www.herongyang.com/Perl/PDF-Full-Version.html - Provides information on how to obtain the full version of this book in PDF, EPUB, or other format.

Perl Tutorials - Herong's Tutorial Examples

∟ Perl on Linux Systems

This chapter provides tutorial examples and notes about using Perl on Linux systems. Topics include verifying Perl installation; running Perl scripts in different ways; making a Perl script file executable.

Perl Installation on Linux Systems

Running Perl Scripts on Linux Systems

Takeaways:

Perl is included in Linux systems. There is no need to install it manually.

The best way to run a Perl script file on a Linux system is to include #!/usr/bin/perl as the first line in the file and change its mode to be executable.

Perl Tutorials - Herong's Tutorial Examples

∟ Perl on Linux Systems

∟ Perl Installation on Linux Systems

This section describes how to verify Perl installation on Linux systems. The 'perl -v' command returns which version of Perl is installed on the Linux system.

If you are running a Linux system, Perl is already installed on the system. No need to do any extra installation work.

Here is what I did to verify the Perl installation on the Linux server of my Internet service provider in 2019:

/home/herong$ which perl

/usr/bin/perl

 

/home/herong$ perl -v

This is perl 5, version 26, subversion 1 (v5.26.1) built for

x86_64-linux-gnu-thread-multi (with 67 registered patches,

see perl -V for more detail)

 

Copyright 1987-2017, Larry Wall

 

Perl may be copied only under the terms of either the Artistic License

or the GNU General Public License, which may be found in the Perl 5

source kit.

 

Complete documentation for Perl, including FAQ lists, should be found

on this system using man perl or perldoc perl.  If you have access

to the Internet, point your browser at http://www.perl.org/, the Perl

Home Page.

 

/home/herong$ man perl

PERL(1)          Perl Programmers Reference Guide          PERL(1)

 

NAME

  perl - The Perl 5 language interpreter

 

SYNOPSIS

  perl [ -sTtuUWX ]      [ -hv ] [ -V[:configvar] ]

      [ -cw ] [ -d[t][:debugger] ] [ -D[number/list] ]

      [ -pna ] [ -Fpattern ] [ -l[octal] ] [ -0[octal/hexadecimal] ]

      [ -Idir ] [ -m[-]module ] [ -M[-]'module...' ] [ -f ]

      [ -C [number/list] ]      [ -S ]      [ -x[dir] ]

      [ -i[extension] ]

      [ [-e|-E] 'command' ] [ -- ] [ programfile ] [ argument ]...

 

  For more information on these options, you can run perldoc perlrun.

 

GETTING HELP

  The perldoc program gives you access to all the documentation that

  comes with Perl.  You can get more documentation, tutorials and

  community support online at .

...

As you can see from the output, this Linux system has Perl 5.26.1 installed and ready to use.

Even on older versions of Linux systems, Perl was included in Linux distribution packages and installed automatically. Here is an example captured on the Linux server of my Internet service provider in 2009

/home/herong$ which perl

/usr/local/bin/perl

 

/home/herong$ perl -v

This is perl, v5.8.8 built for i486-linux-gnu-thread-multi

 

Copyright 1987-2006, Larry Wall

 

...

Here is another example captured on my old PC running a Linux 2.0.30 system in 1999:

/home/herong$ which perl

/usr/bin/perl

 

/home/herong$ perl -v

This is perl, version 5.004_03

 

Copyright 1987-1997, Larry Wall

 

...

Perl Tutorials - Herong's Tutorial Examples

∟ Perl on Linux Systems

∟ Running Perl Scripts on Linux Systems

This section provides a tutorial example on how to run Perl scripts on Linux systems. To make a Perl script file executable, you need to add '#!/usr/bin/perl' to the beginning of the script.

There are many ways to run Perl scripts on Linux:

1. Run the perl command with the Perl script included in the command line. For example, enter the following command line in a shell window:

/home/herong$ perl -e print 'Hello world!';

Hello world!

Note that the above command will not work in some shell windows. For example, in a bash shell window, you will get the following error, because the ! is a reserved character to access an event in the command history.

/home/herong$ perl -e print 'Hello world!';

-bash: !': event not found

To avoid the problem, you can run the above command a sh command window:

/home/herong$ sh

$ perl -e print 'Hello world!';

Hello world!$

Or you can protect ! using escape sequence:

/home/herong$ perl -e print \"Hello world\!\n\";

Hello world!

Or you can use single quotes ('...') to protect the entire Perl script from the shell:

/home/herong$ perl -e 'print Hello world!\n;'

Hello world!

Here is another example of running a Perl script in a single command line:

/home/herong$ perl -e for (\$i=0; \$i<10; \$i++) {print \"\$i\n\";}

0

1

2

3

4

5

6

7

8

9

Note that dollar sign ($) used for Perl scalar variables are also shell reserved characters, we need to use escape sequences to protect them.

Also note that double quote (") is used to put the entire script code as one command line parameter. Any double quote inside the program needs to be protected as (\").

Or you can use single quotes ('...') to protect the entire Perl script from the shell:

/home/herong$ perl -e 'for ($i=0; $i<10; $i++) {print $i\n;}'

0

1

2

3

4

5

6

7

8

9

Including Perl script in the command line is quick and easy. But you can only run scripts that are small enough to fit into one command line.

2. Run the perl command with the Perl script supplied from the standard input stream. For example, enter perl in a command window. Then enter the script code followed by Control-D, which is the End Of File (EOF) indicator:

/home/herong$ perl

$s=0;

for ($i=0; $i<10; $i++) {

  $s+=$i;

}

print $s\n;

^D

 

45

Obviously, you can enter a much longer script in this way. But the program is not save permanently.

3. Run the perl command with the Perl script supplied in a file. For example, enter the following Perl script in a file called hello.prg:

  print Hello world!\n;

Then enter the following command in a command window:

/home/herong$ perl hello.prg

Hello world!

4. Run Perl script files as commands. You can do this, only if you insert a special line at the beginning of your script file: #!/usr/bin/perl, and assign execution permission to the script file. This special line represents the Perl installation location on the file system.

For example, enter the following script in a file called hello.pl:

#!/usr/bin/perl

  print Hello world!\n;

Then assign execution permission and enter the script file name to run it:

/home/herong$ chmod a+x hello.pl

/home/herong$ ./hello.pl

Hello world!

It works! And this is the best way to run Perl scripts on Linux systems.

Perl Tutorials - Herong's Tutorial Examples

∟ ActivePerl on Windows Systems

This chapter provides tutorial examples and notes about using ActivePerl on Windows systems. Topics include features of ActivePerl; installing ActivePerl on Windows systems; running Perl scripts with ActivePerl.

What Is ActivePerl?

Install ActivePerl on Windows Systems

Running Perl Scripts on Windows Systems

Takeaways:

To use Perl script on a Windows system, you need to download and install ActivePerl community version.

The best way to run a Perl script file on a Windows system is to name the file with .pl extension and associate it with ActivePerl program.

Perl Tutorials - Herong's Tutorial Examples

∟ ActivePerl on Windows Systems

∟ What Is ActivePerl?

This section describes what is ActivePerl - a free Perl engine for Windows, Linux and other platforms developed by ActiveState.

ActivePerl is a Perl engine developed by ActiveState supporting multiple platforms including Windows and Linux. ActiveState provides, free to the community, the ActivePerl binary packages, which include:

Perl, the binary core distribution of the Perl engine.

The Perl Package Manager, for installing Perl extension modules.

Complete documentation.

The Windows version of ActivePerl also includes:

PerlScript, an ActiveX scripting engine, like JavaScript or VBScript, with a Perl brain.

Perl for ISAPI, an IIS plug-in that runs Perl CGI scripts faster.

PerlEz, for embedding Perl the easy way.

ActiveState also offers a non-free version, ActivePerl Enterprise, with extra features.

For more information on ActivePerl, visit ActivePerl home page at ActiveState.com/ActivePerl.

Perl Tutorials - Herong's Tutorial Examples

∟ ActivePerl on Windows Systems

∟ Install ActivePerl on Windows Systems

This section provides a tutorial example on how to install ActivePerl on a Windows computer.

If you are using a Windows system and want to run Perl scripts, you can install the free binary package, ActivePerl, provided by ActiveState. Here is what I did to install ActivePerl on my Windows computer.

1. Go to https://www.activestate.com/products/perl/, I see the ActiveState Perl download page.

2. Click on Download Perl 5.32 button. I see the login page.

3. Log in with your ActiveState account, or sign up a new account. I see the new project page.

4. Select Perl > 5.34.0 > Windows 10 and click Create Runtime. I see the Download & Install Runtime comment.

5. Copy the command and run it in a command window:

herong> powershell -Command \

  "& $([scriptblock]::Create((New-Object Net.WebClient).DownloadString \

  ('https://platform.activestate.com/dl/cli/pdli01/install.ps1'))) \

  -activate-default herong/Perl-5.34.0-Windows"

 

- Preparing Installer for State Tool Package Manager... Done

- Installing State Tool Package Manager

 

The State Tool lets you install and manage your language runtimes.

 

ActiveState collects usage statistics and diagnostic data about failures.

By using the State Tool Package Manager you agree to the terms of

ActiveState’s Privacy Policy, available at:

https://www.activestate.com/company/privacy-policy

 

- Downloading State Tool version 0.32.0-SHA7474314...  Done

- Installing State Tool to

  C:\Users\herong\AppData\Local\ActiveState\StateTool\release... Done

4. Open a new command window, and type in perl -v. If you see the following output, your installation is ok.

herong> perl -v

 

This is perl 5, version 34, subversion 0 (v5.34.0) built

  for MSWin32-x64-multi-thread

 

Copyright 1987-2021, Larry Wall

 

Binary build 34.0r4 provided by ActiveState http://www.ActiveState.com

Built Wed Nov 17 04:20:44 2021

 

Perl may be copied only under the terms of either the Artistic License

or the GNU General Public License, which may be found in the Perl 5

source kit.

 

Complete documentation for Perl, including FAQ lists, should be found on

this system using man perl or "perldoc