Nothing huge, but some cleanup things:

• You don't ever use Time::Local. localtime is a built-in function.
• You need my in front of your date/time variable list, to run under strict.
• You don't need 'junk' variables ($j1, $j2, $j3) for the extra values from localtime. If your list on the left has fewer variables than are passed from the right, the extra ones will be discarded.
• Your day and month adjustments can be done shorter and more cleanly with increment operators: $year += 1900; $mon++;
• You should probably do error checking on your mkdir statements.
• It's strange that you're opening your output files once, and then opening them again right away inside your subroutine. In fact, I'd almost expect that to cause an error or warning, but maybe Perl silently closes and re-opens it. Are you doing that so the first open (with '>') will start the files empty, and then switch to appending? It's probably unnecessary, but maybe you could explain your thinking there.
• When you have multiple print statements in a row, you can often clean things up with a here-document:

  print $html_report <<END;
  
  #### Now Analyzing '$file_01_txt'
  
  END
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• When you have "if(this){single_statement}" constructs, you can often eliminate much of the clutter of parens and brackets with postfix syntax:

   print $html_report "$line\n" if $line =~ /search criteria 01/i;
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