I believe that other monks have helped you, but still if you will face the problem of using libA.pm routines in libB.pm and viceversa, (you have to read perlmod, perlmodlib, and 'intermediate perl' book for some reference) for that you need to properly define the reusable routines in the appropriate modules,
when it comes to calling routines, you can have another module Objects.pm which maintains the objects of the other two modules(liba and libb) and this objects.pm will be used to share the objects variable to across libA and libB, so that the calling becomes easy.
Some hints for Objects.pm and example code is below

# register object in objects.pm
sub RegisterObject
{
    my ($Pack,$Object,$Tag) = @_;
    my ($Name);

    $Name = uc($Tag) . 'OBJ';
    $Pack->{'Objects'}->{$Name}->[0] = $Object;
    $Pack->{'Objects'}->{$Name}->[1] = $Tag;

    print STDERR "Registered Object $Tag with Objects Handler\n";    
}
# autoload in object.pm
sub AUTOLOAD
{
    my ($Pack) = shift;
    my ($Type,$Calledas,$Key,$Name);

    if (ref($Pack)) { $Type = ref($Pack); }
    else
    {
        print STDERR "$Pack is not an Object\n";
        exit(1);
    }

    $Calledas = $AUTOLOAD;
    $Calledas =~ s/.*://;

    foreach $Key (keys(%{$Pack->{'Objects'}}))
    {
        if ($Pack->{'Objects'}->{$Key}->[1] eq $Calledas)
        {
            return($Pack->{'Objects'}->{$Key}->[0]);
        }
    }
    print STDERR "%%%%%%% Unregistered Object - AUTOLOAD Called as $Ca
+lledas %%%%%%%%\n";
    
    return(-1);
}
# from your main script register the objects of liba and libb.
# the $main::Objects must be the object of Objects.pm.
    $main::Objects->RegisterObject($BlessedObjectRef, $ObjectName);
# you have to pass $main::Objects to liba and libb during object creat
+ion(probable in new())
# from there on your liba can use libb routines like
$main::Objects->liba->routineX()
# which will call autoload and retrieve the object of liba and call th
+e routineX.
# the same can be used in libb.
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I believe that I haven't confused you, the above is just an example, I hope it will help you
I have been using the above Objects.pm technique for years.
It is helping me to manage multiple module's objects and calling routines among themselves.