I suppose the author of that decided to be a little pedantic about what he defines to be the object named self i.e. The blessed reference as opposed to the anonymous hash or in otherwords, a member of a class as opposed to a plain old data-structure.

You might come across a very simple constructor like the following if all that is needed is to return an instantiated object.

sub new {
   return bless {}, shift;
}
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What I don't see is why the author supposes $class might be a reference in ref $class || $class. The first argument to a constructor is usually always a literal string representing the class name and i'm betting that ref $class is redundant there as it evaluates to false.