Your answer for the 'actual question' works. Thankyou for that. To address your first point I have done the following: 
 if ($file_in_question =~ /^(\d{4})/){
    $year = $1;
  }
  else {
    next;
    }

[download]
Also I would like to say that BrowerUK's explanation offered in the post you refer to, I believe, is very well written. I would encourage anyone here to read it through.

In reply to Re^2: map function - print to file problem by Win
in thread map function - print to file problem by Win

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