use Blah;
use Foobar;

$b = Blah->new();
$f = Foobar->new();
$b->doSomething;

##</code><code>##

sub new {
...
}

sub doSomething {
$f->methodX();
}

##</code><code>##

sub new {
...
}

sub methodX {
does some fun things here
}