# 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 $Calledas %%%%%%%%\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 creation(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 the routineX.
# the same can be used in libb.