# make a new object of type 'Object' and pass it a callback sub
my $obj = new Object( sub{print "Hello World"} );

# call a method on that object
$obj->method;

# when we 'use' an OO module we effectively just add its packages to our code
# so lets just write a little package here that has a callback sub
package Object;
use Data::Dumper;

sub new { 
    my $class    = shift;
    my $callback = shift;
    my $anon_ref = { 'callback' => $callback };
    # make object by blessing our anon hash into $class
    my $object   = bless $anon_ref, $class;
  return $object;
}

sub method {
   my $self = shift;
   print "This is what \$self looks like:\n\n", Dumper($self), "\n\n";
   print "And here is our callback sub in operation\n\n";
   &{$self->{'callback'}};
}