gistfile1.txt

package Encodable;
use Moose::Role;

has encoder => (
  is => 'rw',
  isa => 'CodeRef'
);

sub encode {
   my $self = shift;
   my $thing = shift;

   return $self->encoder->encode($self, $thing);
}

package MyObject;
use Moose;

with 'Encodable';

package main;

my $object = MyObject->new(encoder => sub { .... });
$object->encode("foo");