Constructors and Instance Methods

Still, someone has to know what's in the object. And that someone is the class. It implements methods that the programmer uses to access the object. Here's how to implement the Person class using the standard hash-ref-as-an-object idiom. We'll make a class method called new to act as the constructor, and three object methods called name, age, and peers to get at per-object data hidden away in our anonymous hash. 

    package Person;
    use strict;


    ##################################################
    ## the object constructor (simplistic version)  ##
    ##################################################
    sub new {
        my $self  = {};
        $self->{NAME}   = undef;
        $self->{AGE}    = undef;
        $self->{PEERS}  = [];
        bless($self);           # but see below
        return $self;
    }


    ##############################################
    ## methods to access per-object data        ##
    ##                                          ##
    ## With args, they set the value.  Without  ##
    ## any, they only retrieve it/them.         ##
    ##############################################


    sub name {
        my $self = shift;
        if (@_) { $self->{NAME} = shift }
        return $self->{NAME};
    }


    sub age {
        my $self = shift;
        if (@_) { $self->{AGE} = shift }
        return $self->{AGE};
    }


    sub peers {
        my $self = shift;
        if (@_) { @{ $self->{PEERS} } = @_ }
        return @{ $self->{PEERS} };
    }


    1;  # so the require or use succeeds

We've created three methods to access an object's data, name, age, and peers. These are all substantially similar. If called with an argument, they set the appropriate field; otherwise they return the value held by that field, meaning the value of that hash key.