How do you create and use custom attributes in Perl’s object-oriented programming?

Custom attributes can be useful for adding additional data fields or properties to a Perl object that are not explicitly defined in the object class. Here’s how you can create and use custom attributes in Perl’s object-oriented programming:

1. Define the attribute in the object class using the Class::Accessor module. For example, if you have a class called "Person" and you want to add a custom attribute called "age_group", you can define it like this:

use Class::Accessor;

package Person;
use base qw/Class::Accessor/;

__PACKAGE__->mk_accessors(qw/age_group/);

2. In the constructor method for the class, you can set the value of the custom attribute using the attribute accessor method generated by Class::Accessor. For example:

sub new {
  my $class = shift;
  my $self = {
    name => shift,
    age => shift,
    age_group => '',
  };
  bless $self, $class;
  $self->set_age_group(); # set the age_group attribute based on age
  return $self;
}

sub set_age_group {
  my $self = shift;
  my $age = $self->age;
  if ($age < 18) {
    $self->age_group('Under 18');
  } elsif ($age < 30) {
    $self->age_group('18-29');
  } elsif ($age < 40) {
    $self->age_group('30-39');
  } else {
    $self->age_group('40+');
  }
}

3. To access the custom attribute in other methods, you can use the accessor method generated by Class::Accessor. For example:

sub print_person_info {
  my $self = shift;
  print "Name: " . $self->name . "n";
  print "Age: " . $self->age . "n";
  print "Age group: " . $self->age_group . "n";
}

4. To use the custom attribute outside of the object, you can call the accessor method on the object. For example:

my $person = Person->new('John', 25);
print $person->age_group; # prints "18-29"

By using Class::Accessor and defining custom attributes, you can add additional data fields or properties to your Perl objects and access them easily in your methods.