G'day Perl Beginner01,

Welcome to the monastery.

"An example of encryption is that "a" becomes "z", and "b" becomes "y" and so on, or whatever shifting algorithm you can devise."

Here's an example of that I wrote about nine months ago: "Re: Caesar Cipher". You may find other nodes in that thread have useful information.

For the I/O part, see "perlintro: Files and I/O". While that should have sufficient information for your stated needs, it does provide links to more detailed discussions.