1. Introduction
The two previous lectures supplied you with enough knowledge to know how to program most perl scripts. That is, with some help from the perl man pages, especially the perlfunc one.
If however, you wish to maintain a more complex perl program, you will probably outgrow the functionality that was covered so far. However, perl has certain mechanisms that make it to easier to write code that is more scalable, more modular and more re-usable.
The purpose of a modular code is to make sure there isn't any duplicate code, and that parts of the code can later be used by others, with as little modification as possible. Perl, as most other languages, does not force writing modular code upon the programmer, but it does provide some language mechanisms that help do that.