Perl Programming – Quick Review (Simple & Easy Guide)

Perl is a powerful, flexible, and beginner‑friendly scripting language. It is famous for text processing, regular expressions, system administration, and web development.

This guide explains all important Perl topics in simple English, with easy examples, perfect for students, beginners, and interview preparation.

1. What is Perl?

Perl is a high‑level programming language created by Larry Wall. It is often called the “Swiss Army Knife” of programming because it can do many tasks easily.

Where Perl is used

Text processing
Log file analysis
System administration
Web development (CGI)
Automation scripts

2. Perl Program Structure

A simple Perl program looks like this:

#!/usr/bin/perl
use strict;
use warnings;

print "Hello, World!\n";

Explanation

#!/usr/bin/perl → tells system to use Perl
use strict; → forces good coding rules
use warnings; → shows warning messages
print → prints output

3. Variables in Perl

Perl uses symbols to identify variable types.

Symbol	Type	Example
`$`	Scalar (single value)	`$age = 25;`
`@`	Array (list)	`@nums = (1,2,3);`
`%`	Hash (key‑value)	`%marks = (Math => 90);`

Scalar Variable Example

my $name = "Krishna";
my $age = 22;
print "$name is $age years old\n";

4. Data Types

4.1 Scalars

Store single values (number or string).

my $price = 100;
my $city = "Chennai";

4.2 Arrays

Store multiple values.

my @colors = ("Red", "Green", "Blue");
print $colors[0];   # Red

4.3 Hashes

Store key‑value pairs.

my %student = (
  name => "Raj",
  age  => 21
);
print $student{name};

5. Operators

Arithmetic Operators

my $a = 10;
my $b = 5;
print $a + $b;   # 15

Comparison Operators

==   equal
!=   not equal
>    greater than
<    less than

String Comparison

 eq   equal
 ne   not equal

6. Conditional Statements

if Statement

my $age = 18;
if ($age >= 18) {
    print "Eligible to vote";
}

if‑else

if ($age >= 18) {
    print "Adult";
} else {
    print "Minor";
}

7. Loops in Perl

for Loop

for (my $i = 1; $i <= 5; $i++) {
    print "$i\n";
}

while Loop

my $i = 1;
while ($i <= 3) {
    print "$i\n";
    $i++;
}

foreach Loop

my @nums = (10, 20, 30);
foreach my $n (@nums) {
    print "$n\n";
}

8. Subroutines (Functions)

Subroutines are reusable blocks of code.

sub add {
    my ($a, $b) = @_;
    return $a + $b;
}

print add(5, 3);

9. Strings in Perl

String Concatenation

my $first = "Hello";
my $second = "World";
print $first . " " . $second;

String Length

print length("Perl");

10. Arrays – Important Functions

my @arr = (1,2,3);
push @arr, 4;    # add
pop @arr;        # remove last
shift @arr;      # remove first
unshift @arr, 0; # add first

11. Hash Functions

my %data = (a => 1, b => 2);

my @keys = keys %data;
my @values = values %data;

12. File Handling in Perl

Writing to a File

open(my $fh, '>', 'test.txt');
print $fh "Hello Perl";
close($fh);

Reading from a File

open(my $fh, '<', 'test.txt');
while (<$fh>) {
    print $_;
}
close($fh);

13. Regular Expressions (Regex)

Perl is very famous for regex.

my $text = "I love Perl";
if ($text =~ /Perl/) {
    print "Found";
}

14. Command Line Arguments

my $name = $ARGV[0];
print "Hello $name";

Run:

perl test.pl Krishna

15. Modules in Perl

Modules help reuse code.

use Math::BigInt;

Install module:

cpan Module::Name

16. Object‑Oriented Perl (Basic)

package Person;

sub new {
    my $class = shift;
    return bless {}, $class;
}

1;

17. Advantages of Perl

Very powerful text processing
Easy scripting
Huge library (CPAN)
Cross‑platform

18. Disadvantages of Perl

Code readability can be difficult
Less popular today compared to Python

19. Perl vs Other Languages

Feature	Perl	Python
Text Processing	Excellent	Good
Readability	Medium	Very Good
Speed	Fast	Fast

20. Error Handling in Perl

Error handling helps us find and fix problems in a program.

die Function

open(my $fh, '<', 'nofile.txt') or die "File not found";

If the file does not exist, the program stops and shows the message.

warn Function

warn "This is a warning message";

warn shows a message but does not stop the program.

21. Input from User

Perl can take input from the user using STDIN.

print "Enter your name: ";
my $name = <STDIN>;
chomp($name);
print "Hello $name";

chomp removes the extra newline character.

22. Date and Time in Perl

my $time = localtime();
print "Current time: $time";

Perl can easily handle system date and time.

23. Useful Built‑in Functions

Some commonly used Perl functions:

print uc("perl");     # PERL
print lc("PERL");     # perl
print reverse("abc"); # cba

24. Perl for System Administration

Perl is widely used by system admins.

Example: Run System Command

my $files = `ls`;
print $files;

This command lists files in the current directory.

25. Web Programming with Perl (Basic Idea)

Perl is used in CGI scripts for web applications.

print "Content-type: text/html

";
print "<h1>Hello from Perl</h1>";

26. Interview Important Points

Perl variables use symbols $ @ %
Perl is best known for regular expressions
CPAN is Perl’s module repository
strict and warnings improve code quality

27. Real‑World Use Cases of Perl

Parsing log files
Data extraction
Automation scripts
Report generation
Bioinformatics

28. Best Practices in Perl

Always use strict and warnings
Write readable code
Use comments for clarity
Reuse code using modules

29. Learning Path for Beginners

Learn Perl syntax
Practice arrays and hashes
Master regex
Learn file handling
Explore CPAN modules

30. Conclusion

Perl is a mature, stable, and powerful scripting language. Even today, it is widely used for text processing, automation, and system tasks. Its strong regular expression support makes it unique compared to other languages.

For beginners, Perl builds a strong foundation in scripting and problem solving. For professionals, it remains a reliable tool for real‑world automation.

If you are preparing for interviews, exams, or practical projects, learning Perl is still a valuable skill.