...
  {
    # create the file, must be world-writable
    my $temp = MyApp::Local->umask(0);
    my $fh;
    sysopen($fh, $path, O_WRONLY | O_CREAT | O_EXCL, 0666)
        or die "$path: $!\n";
    close $fh;
    # umask restored when $temp goes out of scope, even by dying
  }
  ...