my %matches = (
  ENG      => 'EN',
  AVN      => 'AV',
  TRAN     => 'TN',
  QM       => 'QM',
  MI       => 'MI',
  POLICE   => 'MP',
  MP       => 'MP',
  CHAPLAIN => 'CH',
  INF      => 'IN',
  FA       => 'FA',
  MED      => 'MD',
  SIG      => 'SC',
  MAIN     => 'SS',
  AR       => 'AR',
);
if ( exists ( $match{uc($row[4])} ) {
  $row[3] = $match{uc($row[4])};
} else {
  $row[3] = 'PU';
}