Reasoning why knowing the system paths is a good idea can be found here. Now let's see how one can guess (get?) them in Perl.
There are a lot of Perl installation made to non-standard paths. Like:
I was trying to find out what do this installations share and what could be used to find out if the Perl is in file hierarchy standard folder - /usr/bin/perl. The simplest way, that I found out, was to:
use Config;
if ($Config::Config{'prefix'} eq '/usr') { ... do stuff ... }
That is basically all Sys::Path does. If the installation prefix was set to "/usr" (in all Linux distributions standard Perl packages it is), than the rest of system paths is by default set to FHS. If not all of the paths are based on the prefix - $PREFIX/etc, etc.
Just check the Pod of Sys::Path for all the different paths and their usage.
too simple? but works :-)