We've created a tie() class, and a program that uses it. You can customize this tie() class as much as you want: adding multiple 'mode' levels, adding manually invoked methods to change the password file or level of clobbering, making reading/writing from the resource more efficient, file syncing, real-time read/write operations, or almost anything else you can think up.
I encourage you to write your own class that ties to a directory, the Windows registry, config files, remote machines, or system commands. All are straightforward applications of the techniques in this article.
I hope you now have a better understanding of how tie() works, how to use it, have enough information to write your own tie module, and now have another tool of Perl to use in your programming.