sub color {
  my $shift;
  if (@_) {              # are there any more parameters?
    # yes, it's a setter:
    $self->{Color} = shift;
  } else {
    # no, it's a getter:
    $self->{Color};
  }
}

Now you can say:

my $tv_horse = Horse->named("Mr. Ed");
$tv_horse->color("black-and-white");
print $tv_horse->name, " is colored ", $tv_horse->color, "\n";

The presence of the parameter in the second line denotes that you are setting the color, while its absence in the third line indicates a getter.