Thanks a lot for the explanation. One more thing to understand. Am I right to say that $# equals to $#_ and means the last index in array?

You've removed your original post. That makes this thread look very weird for anyone who hasn't looked and remembered your original post.

As for you question, the answer is no for the first part, and yes for the second. But since you original content is gone, the context is gone, and I cannot explain things further.