use strict;
use warnings;

my($status);
tie $status, 'Status';

$status = 'ungnown'; # warning, and value does not get set.
$status = 'good'; # works

print "$status";

package Status;
use Tie::Scalar;
use Carp;
use base qw(Tie::StdScalar);

sub TIESCALAR {
	my $class = shift;
	my $status = shift;
	
	bless \$status, $class;
}

sub STORE
{
   my($me, $value) = @_;
   unless ($value eq 'good'){
      warn("invalid status: $value. Status not set");
	  return undef;
   }
   ${$me} = $value;
}

sub FETCH
{
   my($status) = @_;
   return ${$status};
}