while (defined($_ = readdir(AUDDIR))) {
    next if /^\.\.?$/;
    unless (delete $files{$_}) {
      open(FH, "<$_") or die "Can't open file $_: $!\n";
      flock(FH, LOCK_EX) or warn "Can't get exclusive lock on file $_ : $!\n";
      close(FH);
    }
}

##</code><code>##

Can't get exclusive lock on file ora_6688.aud : Bad file number