I had some time to think about it, and realized that my code isn't valid. My earlier example depends on a race condition to select one state or the other. What I _should_ have done is implement a solution that acts both ways without interference:
my $folly = $fool->folly;
my $tabby = new Cat( owner => 'Schroedinger' );
answer( $folly ) if ( $tabby->alive );
answer( not $folly ) unless ( $tabby->alive );
The problem I've been running into is that the first time I call Cat::alive(), the quantum decoherence collapses, and it only invokes answer() once.
Does anyone have a method for measuring the "alive" state of $tabby without actually looking into the box? I think I need to modify the implementation of sub alive() ...