What you need is at least partially an adaptation of Inside-out objects.

# note the package level shared hash; this will store the 
# actual values of the active attribute.
my %active : shared;

# CONSTRUCTOR
sub new {
 local *IN;
 my $self = {};
 $self->{active} = \$active{$self} = 1;                    # This vari
+able must be shared between threads.
 $self->{in} = undef;
 $self->{thread} = undef;
 open(*IN, "a_program" ) or ${$self->{active}} = 0;
 $self->{in} = *IN;
 $self->{thread} = threads->new(\&reader, $self);      # Start thread
 bless($self);
 return $self;
}
[download]

Then you can access the shared value as ${$self->{active}}, or as $active{$self} if you're in the package...

At least, I think this will work; it would be nice if I had 5.8.0 installed here to test it :)
--
Mike