my @match_flds = /(\d{4}) \s
                  (\d{5}) \s
                  (\d{3}) \s
                  (\d{2}) \s
                  (\d{2} \/ \d{2} \/ \d{2}) \s
                  (\d{2} \: \d{2} \: \d{2}) \s
                  (\d{3}) \s
                  (\d{2}) \s
                  (\S+)   \s
                  (\d{2}) \s
                  (\d{2}) \s
                  (\d{2}) \s
                  (\d{2}) \s
                  (\w{3}) $ /x ;
if (@match_flds) {
  # now indexes are 1-off from the corresponding numbered
  # regex vars: e.g., $match_flds[0] is $1, $match_flds[1] is $2, etc.

  # remap the 15th field using your hash
  $match_flds[14] = $TOC{ $match_flds[14] };

  # print them
  print join( ' ', @match_flds ), "\n";
}