package Foo;

sub do_it
{
  my $self = shift;
  my $do_it_to = shift;

  $do_it_to->handler(sub { $self->logger(@_) });
}

# and other stuff, like sub logger.

package Bar;

sub handler
{
  my $self = shift;
  my $callback = shift;

  for ($self->get_all_items())
  {
    $callback->($_);
  }
}