package MyMother;
use strict;
use vars qw/@ISA/;
use Exporter;
@ISA = qw/Exporter/;

sub new {
   my ($class, @args) = @_;
   my $self = { MODIFIED => 0,
                TYPE => $args[0],
              };
   bless $self, $class
}

sub modified { $_[0]->{MODIFIED} }

##</code><code>##

package MyChild;
use strict;
use vars qw/@ISA/;
use MyMother;
@ISA = qw/MyMother/;

sub new {
   my ($class, @args) = @_;
   my $self = $class->SUPER::new(@args);
   bless $self, $class;
   if ($self->{TYPE} == 1) {
     $self->modified = sub { 0 };
   }
   $self;
}

##</code><code>##

#!/usr/bin/perl -wd
use MyChild;
my $ch = MyChild->new(2);
$ch->{MODIFIED} = 1;
print $ch->modified."\n";
$ch = MyChild->new(1);
$ch->{MODIFIED} = 1;
print $ch->modified."\n";