I would highly recommend reading Damian Conway's Book Object-Oriented Perl for a project like this. Just flipping through my copy, I came accross this example on page 92, where he address the issue of data hiding by using the AUTOLOAD function.

package CD::Music;
use strict;
use vars '$AUTOLOAD';  # Keep 'use strict' happy

{
  my %_attrs =
    ( _name       => undef,
      _artist     => undef,
      _publisher  => undef,
      _ISBN       => undef,
      _tracks     => undef,
      _rating     => undef,
      _room       => undef,
      _shelf      => undef,
    );
  
  sub _accessible { exists $_attrs{$_[1]} }
}

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);
}
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This will dynamically create methods such as getname to access the underlying data, rather than letting someone poke at it willy-nilly. This keeps your access methods and your data in sync. It also allows for easier error checking, since all your methods are being dynamically defined in one place.

-Blake