my $st = File::stat::stat($path) or die "Cannot access $path: $!\n";
my $key_text = join(":", $path, $st->dev, $st->ino, $st->mtime);
my $st = File::stat::stat($path) or die "Cannot access $path: $!\n";
my $key_text = join(":", $path, $st->dev, $st->ino, $st->mtime);