package PackageA;

require "libraries/somelib.pl";

... variables, functions, etc
1;

##</code><code>##

package PackageB;

require "libraries/somelib.pl"; #NOTE: Same library as included in packageA

... variables, functions, etc
1;

##</code><code>##

#!/usr/bin/perl -w

use strict;
use PackageA;
use PackageB;