sub done {
    my $self = shift;
    return not $self->foo and not $self->bar; # gotcha!
}

##</code><code>##

    (return not $self->foo) and not $self->bar;

##</code><code>##

sub done {
    my $self = shift;
    return !$self->foo && !$self->bar; 
}

##</code><code>##

    my $bool = 1 and 0;
    # $bool == 1 and $_ == 0; may not be what you expect!