}
    elsif (!exists $self->{_parts} || ref($self->{_content}) eq "SCALAR") {
	$self->_parts;
    }

    push(@{$self->{_parts}}, @_);
    _stale_content($self);
    return;
}

sub _stale_content {
    my $self = shift;
    if (ref($self->{_content}) eq "SCALAR") {
	# must recalculate now
	$self->_content;
    }
    else {
	# just invalidate cache
	delete $self->{_content};
	delete $self->{_content_ref};
    }
}


# delegate all other method calls the the _headers object.
sub AUTOLOAD
{
    my $method = substr($AUTOLOAD, rindex($AUTOLOAD, '::')+2);

    # We create the function here so that it will not need to be
    # autoloaded the next time.
    no strict 'refs';
    *$method = sub { shift->{'_headers'}->$method(@_) };
    goto &$method;
}


sub DESTROY {}  # avoid AUTOLOADing it


# Private method to access members in %$self
sub _elem
{
    my $self = shift;
    my $elem = shift;
    my $old = $self->{$elem};
    $self->{$elem} = $_[0] if @_;
    return $old;
}


# Create private _parts attribute from current _content
sub _parts {
    my $self = shift;
    my $ct = $self->content_type;
    if ($ct =~ m,^multipart/,) {
	require HTTP::Headers::Util;
	my @h = HTTP::Headers::Util::split_header_words($self->header("Content-Type"));
	die "Assert" unless @h;
	my %h = @{$h[0]};
	if (defined(my $b = $h{boundary})) {
	    my $str = $self->content;
	    $str =~ s/\r?\n--\Q$b\E--\r?\n.*//s;
	    if ($str =~ s/(^|.*?\r?\n)--\Q$b\E\r?\n//s) {
		$self->{_parts} = [map HTTP::Message->parse($_),
				   split(/\r?\n--\Q$b\E\r?\n/, $str)]
	    }
	}
    }
    elsif ($ct eq "message/http") {
	require HTTP::Request;
	require HTTP::Response;
	my $content = $self->content;
	my $class = ($content =~ m,^(HTTP/.*)\n,) ?
	    "HTTP::Response" : "HTTP::Request";
	$self->{_parts} = [$class->parse($content)];
    }
    elsif ($ct =~ m,^message/,) {
	$self->{_parts} = [ HTTP::Message->parse($self->content) ];
    }

    $self->{_parts} ||= [];
}


# Create private _content attribute from current _parts
sub _content {
    my $self = shift;
    my $ct = $self->header("Content-Type") || "multipart/mixed";
    if ($ct =~ m,^\s*message/,i) {
	_set_content($self, $self->{_parts}[0]->as_string($CRLF), 1);
	return;
    }

    require HTTP::Headers::Util;
    my @v = HTTP::Headers::Util::split_header_words($ct);
    Carp::carp("Multiple Content-Type headers") if @v > 1;
    @v = @{$v[0]};

    my $boundary;