Bug : Mail::Message::Head::FieldGroup::attach stringifies object

Hi all!

I was trying to find out, why this documented piece of 
code doesn't work:

my $sg = new Mail::Message::Head::SpamGroup(software => 
'MINE');
my $own_sg = $head->addSpamGroup($sg);

dying with the:

Can't use string ("Mail::Message::Head::SpamGroup") as a 
HASH ref while "strict refs" in use at 
/spool/timur/perllib/Mail/Message/Head/FieldGroup.pm line 
56, <GEN0> line 163.

Bogus, isn't it?

So, after an hour with debugger it was tracked down to the 
Mail::Message::Head::FieldGroup::attach method, which is 
implemented like:

sub attach($)
{   my ($self, $head) = @_;
     my $lg = ref($self)->clone;
     $self->{MMHF_head} = $head;

     $head->add($_->clone) for $self->fields;
     $lg;
}

It seems, that taking ref($self) here is unnecessary :) At 
least, that's the root of that evil stringification..

With regards,
Timur Bakeyev.