package Trait::LifeGuard;

sub swim {
  return Trait::LifeGuard::_swim();
}

sub save_drowning_swimmer {
  my (undef, $swimmer) = @_;
  # save the swimmer
}

1;

package Trait::Dog;

Class::Trait->expects('doggie_treat');

sub swim {
  # $class might actually be an instance, but we should assume
  # nothing about the internals of the object
  my ($class, $target) = @_;
  Trait::Dog::_eat($class->doggie_treat);
  # swim to $target
}

sub _eat {
  # this must be called via a fully qualified name because private
  # methods are not flattened into the primary class
}

1;