use strict;
use warnings;
package Music;
use Carp;
our $AUTOLOAD;

{
    my %_attrs =
      (    _name        => undef,
        _artist        => undef,
        _publisher    => undef,
        _ISBN        => undef,
        _tracks        => undef,
        _rating        => undef,
        _room        => undef,
        _shelf        => undef,
      );

    sub _accessible { exists $_attrs{$_[1]}}
}
{    
    my $_count = 0;                        # These are class methods.
    sub get_count { $_count }                # This method is global t
+o the program
    my $_incr_count = sub { ++$_count };        
                                        

sub new                                    # Constructor called "new"
{
    my ($class) = @_;                        # Gets class passed to co
+nstructor
    $_incr_count->();
    bless {                                # Creates a blessed referen
+ce...
            _name        => $_[1],            #
            _artist        => $_[2],            #
            _publisher    => $_[3],            #
            _ISBN        => $_[4],            #
            _tracks        => $_[5],            # Simply assigns hash 
+key variables to
            _room        => $_[6],            # the arguments passed t
+o the constructor.
            _shelf        => $_[7],            #
            _rating        => $_[8],            #
            _read_count    => 0,
        }, $class;                        # in this class
}
}

sub AUTOLOAD {
    my ($self) = @_;
    $AUTOLOAD =~ /.*::get(_\w+)/
        or croak "No such method: $AUTOLOAD";
    $self->_accessible($1)
        or croak "No such attribute: $1";
    $self->{_read_count}++;
    return $self->{$1}
}
        
sub get_location    {($_[0]->{_room}, $_[0]->{_shelf})    }


sub set_location {
    my ($self, $shelf, $room) = @_;            
    $self->{_room} = $room;            
    $self->{_shelf} = $shelf;        
}

sub set_rating {
    my ($self, $rating) = @_;
    $self->{_rating} = $rating;
}

1;
[download]

$PM = "Perl Monk's";
$MCF = "Most Clueless Friar Abbot Bishop";
$nysus = $PM . $MCF;
Click here if you love Perl Monks

Inheritance.

package Person;

sub eat { ... }
sub drink { ... }


package Alcoholic;

@ISA = qw( Person );
sub drink { ... }
[download]

Here, an Alcoholic object has its own drink method, but it inherits the eat method from Person. Similarly, something that inherits from the class you've posted could have its own _accessible method.

japhy -- Perl and Regex Hacker