if ($obj->error) {
    $obj->log_error;
  }

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I assume that you are referring to some of the logging modules out there that do this (eg, Log::Log4perl). In the simple case I agree with you (and it's actually what most of them do behind the scenes anyway). But the problem occurs when you have a computationally expensive error string. For instance: 
  use Data::Dumper;
  $obj->log_error(Dumper($some_very_large_structure));

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By using the first approach, this expensive call could be avoided if the object just gave you an accessor so that you could make the decision yourself if the logging was necessary.

-- More people are killed every year by pigs than by sharks, which shows you how good we are at evaluating risk. -- Bruce Schneier

In reply to Re^2: "Accessors (don't always) break encapsulation" by mpeters
in thread "Accessors break encapsulation"? by tlm

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