{
        my %SELF = (
                foo => 0,
                bar => "",
                baz => [],
        );
        sub new {
            my $self = bless {} => shift;
            my %p = @_;

            croak("...") if keys %p > keys %SELF;
            # If given a bad key.

            $self->$_($p{$_}) foreach keys %p; # Lazy. Damn lazy.

            return $self;
        }
    }