> But now you have also the @permitted
    > array, which would allow you to write pack as follows,
    > giving you control over the order in
    > which the elements are packed: 
    > 
    > 
    > sub pack {
    >     my $self=shift;
    >     my $record=join(':', @{$self}{@permitted});
    >     return $record;
    > }