my @attributes = qw(color speed);

# generate the methods
foreach my $attribute (@attributes) {

  my $code = sub {
    # for a better way, see Tanktalus' post below
    my ($self, $value) = @_;
    $self->{$attribute} = $value if defined $value;
    return $self->{$attribute};
  };

  no strict 'refs';
  *{ $attribute } = $code;

} # foreach