$obj->header('My Header', 'value');   # Set 
$obj->header('My Header') = 'value';  # Set
if ($obj->header('My Header') eq 'value' ) {  # Get
...

##</code><code>##

sub header : lvalue {
    my ( $self, $h, $value ) = @_;

    if ( @_ == 1 ) {
        return $self->{header};
    }
    $self->{header}->{$h} = $value
      if defined $value;
    $self->{header}->{$h};
}