How to Learn Perl Object Oriented Programming?

The Object Oriented concept in Perl is very much based on references and anonymous array and hashes. Let's start learning basic concepts of Object Oriented Perl.
Object Basics

In Perl, a package is a self-contained unit of user-defined variables and subroutines, which can be re-used over and over again. Perl Packages provide a separate namespace within a Perl program which keeps subroutines and variables independent from conflicting with those in other packages.

To declare a class named Person in Perl we do:

package Person;

Let's create our constructor for our Person class using a Perl hash reference. When creating an object, you need to supply a constructor, which is a subroutine within a package that returns an object reference. The object reference is created by blessing a reference to the package's class.

#!/usr/bin/perl 

package Person;

sub new {
   my $class = shift;
   my $self = {
      _firstName => shift,
      _lastName  => shift,
      _ssn       => shift,
   };
   # Print all the values just for clarification.
   print "First Name is $self->{_firstName}\n";
   print "Last Name is $self->{_lastName}\n";
   print "SSN is $self->{_ssn}\n";
   bless $self, $class;
   return $self;
}
sub setFirstName {
   my ( $self, $firstName ) = @_;
   $self->{_firstName} = $firstName if defined($firstName);
   return $self->{_firstName};
}

sub getFirstName {
   my( $self ) = @_;
   return $self->{_firstName};
}
1;

Now let's make use of Person object in scientific-employee.pl file as follows:

#!/usr/bin/perl

use Person;

$object = new Person( "Sci", "Pro", 23234345);
# Get first name which is set using constructor.
$firstName = $object->getFirstName();

print "Before Setting First Name is : $firstName\n";

# Now Set first name using helper function.
$object->setFirstName( "Scientific" );

# Now get first name set by helper function.
$firstName = $object->getFirstName();
print "Before Setting First Name is : $firstName\n";

When we execute above program, it produces the following result −

First Name is Scientific
Last Name is Pro
SSN is 124567890
Before Setting First Name is : Sci
Before Setting First Name is : Pro.

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