First of all I agree with the various thoughts and points you make. So let me just comment on the example.

I see what you mean. Aesthetically I don't like the exit condition being woven through the logic, what happens if some day you want to have this cache updating be part of a longer-running script? Also reading the logic through I saw a lot of combinations of actions being taken, but it was not at all obvious why some of them were. And the nesting is pretty darned deep.

I used an indicator variable to do the actions and restructured. Comments? 

{
  ## main loop
  my $cache = 'current';  # Hope for the best
  if (not cache_is_good()) {
    $cache = 'stale';  # Changed expectations
    if (i_am_the_writer()) {
      if (cache_is_stale()) {
        unless (start_background_update()) {
          $cache = 'current'; # Gotta do it foreground
        }
      }
      else {
        $cache = 'current'; # Have nothing to show, gotta do it
      }
    }
    elsif(not cache_is_stale()) {
      # Stuck, gotta retry
      close_cache();
      sleep 5;
      redo;
    }

    update_cache() if $cache eq 'current'; # Make it so
  }
  show_cache($cache);
}

sub start_background_update {
  # NOTE: Uses implicit returns.
  if (i_can_fork()) {
    unless (i_am_the_parent()) {
      be_a_child();
      update_cache();
      exit 0;
    }
  }
}

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UPDATE
Yeah, I know. I was using implicit returns without a comment. At the time it made sense, but that is the kind of thing I rethink and mention shortly after...

In reply to RE (tilly) 1: On elegant coding... by tilly
in thread Just thinking ... by toadi

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