Introduction to PERL Programming

What is Perl?

Perl is a programming language especially  designed for text editing. It is now widely used for a variety of purposes including Linux system administration, network programming, web development etc.
Perl is of great importance in a Linux operating system where it can be used to create programs, handle Databases and e-mails, GUI (Graphical User Interface) development, Networking and System Administration.

 

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PERL V/s Shell Scripting

Even though, shell scripting is available to programmers, they prefer Perl because:

• Programming on Perl does not cause portability issues, which is common when using different shells in shell scripting.
• Error handling is very easy on Perl
• You can write long and complex programs on Perl easily due to its vastness. This is in contrast with Shell that does not support namespaces , modules , object , inheritance etc.
• Shell has fewer reusable libraries available . Nothing compared to Perl's CPAN
• Shell is less secure. Its calls external functions(commands like mv , cp etc depend on the shell being used) . On the contrary PERL does useful work while using internal functions.

Perl Basics

Always start your script with  
#!/usr/bin/perl
It directs the execution to Perl interpreter on your system.

The path is usually the same on most of the Linux distributions.
 

Storing Variables, Input and Output

Action	Description	Syntax	Example
Defining a Variable value	Storing values to a Variable in form of string and number	$variable = "value";	$name = "Ronald";
Output in Perl	If you want a string or a value to display on the screen then you can use the print command	print ("value to be printed") ;	Print("thanks");
Input in Perl	If you want a user input to be assigned to a variable use	$variable = ;	$username = ;

Important points

• With this, if you want the Perl interpreter to ignore a statement, prefix it with a # symbol.
• Remember that every statement in Perl ends with a semi-colon.
• Perl is case-sensitive . Make sure you use the right case.
• You can use any text editor to write your PERL scripts.
• You should then save the script file in .pl extension which will make it recognizable.
• Make sure you do not use spaces when you are naming the Perl script file.

 

Creating a PERL Script

Let us understand the steps in creating a PERL Script
 

1. Create a file using a vi editor(or any other editor).  Name  script file with extension .pl
2. Start the script with #! /bin/perl
3. Write some code.
4. Save the script file  as filename.pl
5. For executing the script type perl filename.pl

 
Let's write a PERL script which will take input from the user and display it back through the script.
#!/usr/bin/perl
print("May I take your name please?") ;
$name = ;

print("Thank you $name");
 
Let's see the steps to create this script -

Summary:

• Perl is a general-purpose programming language originally developed for text manipulation
• Now used for a wide range of tasks including system administration, web development, network programming, GUI development, and more.
• Perl files have .pl extension
• There are three types of variables in Perl, Scalar, Lists and Hashes.