sub STATUS_GOOD    () { 0 }
sub STATUS_BAD     () { 1 }
sub STATUS_UNKNOWN () { 2 }

sub set_status {
   my ($self, $status) = @_;
   $self->{status} = STATUS_GOOD   if $status eq 'good';
   $self->{status} = STATUS_BAD    if $status eq 'bad';
   $self->{status} = STATUS_UNKOWN if $status eq 'unknown';
   require Carp;
   Carp::croak("Unknown status");
}

sub is_good    { return shift->{status} == STATUS_GOOD;    }
sub is_bad     { return shift->{status} == STATUS_BAD;     }
sub is_unknown { return shift->{status} == STATUS_UNKNOWN; }