package Callback;

sub do_callback {
  my $coderef = shift;
  $coderef->(@_);
}

1;

##</code><code>##

package Parent;
use Callback;

sub new { bless {}, shift }

sub do_something { ... }

sub init
{
  my $self = shift;
  my $coderef = \&do_something;
  Callback::do_callback($coderef, $self);
}

1;

##</code><code>##

package Child;
use base qw(Parent);

sub do_something { ... }

1;

##</code><code>##

my $child = Child->new;

##</code><code>##

  $obj->$coderef()