TIMOTOWTDI, search for "INC" or "lib" in perlrun

e.g.

       -f   Disable executing $Config{sitelib}/sitecustomize.pl at sta
+rtup.

            Perl can be built so that it by default will try to execut
+e
            $Config{sitelib}/sitecustomize.pl at startup.  This is a h
+ook that
            allows the sysadmin to customize how perl behaves.  It can
+ for
            instance be used to add entries to the @INC array to make 
+perl
            find modules in non-standard locations.
[download]

But I suppose most sys-admins (if they don't provide an own build) just adjust the default ENV of the users.

updates

site_perl

running perl -V shows me that my system perl was build with /usr/local/lib/site_perl as last entry in @INC.

This points to a yet not existing directory.

Populating or linking should help customizing your system's Perl.

older discussions

HowTo search: "system wide Adding a lib path to perl"

Add directry to @INC system wide

http://stackoverflow.com/questions/2518679/how-can-i-add-a-directory-to-the-perl-library-path-at-the-system-level