A couple of comments. I'm assuming that you are declaring the variable $total_time on line 8. But you are not really using it to do anything besides make a copy of $all_minutes so:

    $all_minutes = $total_hours + $total_minutes;
    $total_time = $total_time + $all_minutes;
    $total_time_hours += int($total_time / 60);
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can be optimized like this:

    $all_minutes = $total_hours + $total_minutes;
    $total_time_hours = int($all_minutes / 60);
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also the lines

   $row[0] = " " if($row[0] eq "");
   $row[1] = " " if($row[1] eq "");
   $row[2] = " " if($row[2] eq "");
   etc..
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could be rewritten as:

   foreach $item(@row){
      $item = " " if($item eq "");
   }
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BTW: I'm not criticizing the way you code, just offering tips to help you with maintainence and readability. So please don't take offence.