The point people are trying to make is that the file naming specifies nothing about the relationship between the classes.

These file layouts are all valid:

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
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It's what's inside the files that determines inheritance, not the names of the files themselves.

Include the following before you use any of your private modules:

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

#!/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();
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