Perl is a widespread programming language and one of its major advantages is that it supports the so-called modules - short bits of code that contain subroutines and perform a number of tasks. The practical side of employing modules is the fact that you do not have to write custom code or include the whole code for a particular task every single time it should be performed. Instead, you can add only a single line in your Perl script that calls a particular module, which in turn will perform the necessary task. Not only will this give you shorter and improved scripts, but it'll also enable you to make changes swifter and much easier. In case you aren't a programmer, but you'd like to work with a Perl app which you've discovered online, for instance, it's very likely that the app will require certain modules to be already set up on the website hosting server.