A.pm
B.pm

A.pm
A/B.pm

B.pm
B/A.pm

AB/A.pm
AB/B.pm

Foo/A.pm
Foo/Bar/B.pm

##</code><code>##

BEGIN { push(@INC, $ENV{'HOME'} . '/lib'); }

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;

BEGIN { push(@INC, $ENV{'HOME'} . '/lib'); }

use Foo::A;
use Foo::Bar::B;

my $a = Foo::A->new();
my $b = Foo::Bar::B->new();