In practical terms, what this means is you can choose a particular module that provides functionality you’d like on your site, and the JSAN system will automatically download and install not only the files for that module, but also the files of any modules upon which that module depends. With the files installed in your site’s directory structure, you can then go ahead and use the functionality they provide in your own scripts.
As JSAN was conceived by Perl hackers, the automated system for downloading and installing JSAN modules is naturally written in Perl. If you’re a developer who works on a Windows box, I sympathise with that groan you just let out. If it’s any consolation, there are rumblings of an “alternative JSAN client” in the works, so fingers crossed. In the meantime, you need to install Perl and get familiar with your operating system’s command prompt before you can install and use JSAN.
If you do use the official client, you’ll benefit from a standardized directory structure, which will let you use JSAN’s built-in import mechanism for scripts. A trick I first saw in the jsolait library for XML-RPC, the system allows a script to load another script that it requires on-the-fly, instead of requiring the Web developer to load that script with a separate