=item $mess->decode

This method tries to replace the content of the message with the
decoded version and removes the C<Content-Encoding> header.  Return
TRUE if successful and FALSE if not.

If the message does not have a C<Content-Encoding> header this method
does nothing and returns TRUE.

Note that the content of the message is still bytes after this method
has been called and you still need to call decoded_content() if you
want to process its content as a string.

=item $mess->encode( $encoding, ... )

Apply the given encodings to the content of the message.  Returns TRUE
if successful. Currently supported encodings are "gzip", "deflate",
"x-bzip2" and "base64".

A successful call to this function will set the C<Content-Encoding>
header.

Note that C<multipart/*> or C<message/*> messages can't be encoded and
this method will croak if you try.

=item $mess->parts

=item $mess->parts( @parts )

=item $mess->parts( \@parts )

Messages can be composite, i.e. contain other messages.  The composite
messages have a content type of C<multipart/*> or C<message/*>.  This
method give access to the contained messages.

The argumentless form will return a list of C<HTTP::Message> objects.
If the content type of $msg is not C<multipart/*> or C<message/*> then
this will return the empty list.  In scalar context only the first
object is returned.  The returned message parts should be regarded as
read-only (future versions of this library might make it possible
to modify the parent by modifying the parts).

If the content type of $msg is C<message/*> then there will only be
one part returned.

If the content type is C<message/http>, then the return value will be
either an C<HTTP::Request> or an C<HTTP::Response> object.

If an @parts argument is given, then the content of the message will be
modified. The array reference form is provided so that an empty list
can be provided.  The @parts array should contain C<HTTP::Message>
objects.  The @parts objects are owned by $mess after this call and
should not be modified or made part of other messages.

When updating the message with this method and the old content type of
$mess is not C<multipart/*> or C<message/*>, then the content type is
set to C<multipart/mixed> and all other content headers are cleared.

This method will croak if the content type is C<message/*> and more
than one part is provided.

=item $mess->add_part( $part )

This will add a part to a message.  The $part argument should be
another C<HTTP::Message> object.  If the previous content type of
$mess is not C<multipart/*> then the old content (together with all
content headers) will be made part #1 and the content type made
C<multipart/mixed> before the new part is added.  The $part object is
owned by $mess after this call and should not be modified or made part
of other messages.

There is no return value.

=item $mess->clear

Will clear the headers and set the content to the empty string.  There
is no return value

=item $mess->protocol

=item $mess->protocol( $proto )

Sets the HTTP protocol used for the message.  The protocol() is a string
like C<HTTP/1.0> or C<HTTP/1.1>.

=item $mess->clone

Returns a copy of the message object.

=item $mess->as_string

=item $mess->as_string( $eol )

Returns the message formatted as a single string.

The optional $eol parameter specifies the line ending sequence to use.
The default is "\n".  If no $eol is given then as_string will ensure
that the returned string is newline terminated (even when the message
content is not).  No extra newline is appended if an explicit $eol is