For Question 3, see perlfaq8.
It details a few ways to add to the INC array....
How do I add a directory to my include path (@INC) at runtime?
Here are the suggested ways of modifying your include path:
the PERLLIB environment variable
the PERL5LIB environment variable
the perl -Idir command line flag
the use lib pragma, as in
use lib "$ENV{HOME}/myown_perllib";
The latter is particularly useful because it knows about machine
dependent architectures. The lib.pm pragmatic module was first included
with the 5.002 release of Perl.