{
  my $need;
  ...
  if ( flock( $LOCK, LOCK_SH ) )         ## Get a copy of Global data
  {   $need = $hash{"stuff"};
      flock( $LOCK, LOCK_UN );
  }
  else { die "$!\n"; }
  ...
  if ( flock( $LOCK, LOCK_EX ) )         ## Update the Global data
  {   $hash{"stuff"} = $need;
      flock( $LOCK, LOCK_UN );
  }
  else { die "$!\n"; }
  ...
}