{
    package SaneFoo;
    use Carp;
    
    my %Foo = ();
    
    sub new {
        my $self = bless {}, shift;
        $Foo{$self} = Foo->new;
        return($self);
    };
    
    sub allows {
        my ($self, $method) = @_;
        return( $method eq "sane" );
    };
    
    sub AUTOLOAD {
        my $self = shift;
        our $AUTOLOAD;
        my ($method) = ($AUTOLOAD =~ m/([^:]+)$/);
        croak "$self cannot $method" unless $self->allows($method);
        $Foo{$self}->$method;
    };
                        
    sub DESTROY {
        my $self = shift;
        delete $Foo{$self};
    };
};