=encoding utf8

=head1 NAME

Mail::Message::Field::Structured - one line of a structured message header

=head1 INHERITANCE

 Mail::Message::Field::Structured
   is a Mail::Message::Field::Full
   is a Mail::Message::Field
   is a Mail::Reporter

 Mail::Message::Field::Structured is extended by
   Mail::Message::Field::Addresses
   Mail::Message::Field::AuthResults
   Mail::Message::Field::DKIM
   Mail::Message::Field::Date
   Mail::Message::Field::URIs

=head1 SYNOPSIS

  my $f = Mail::Message::Field::Full
             ->new('Content-Type' => 'text/html');

  my @encode = (charset => 'jp', use_continuations => 1);
  $f->attribute('filename=passwd');
  $f->attribute(filename => 'passwd', @encode);

  my $attr = Mail::Message::Field::Attribute->new(...);
  $f->attribute($attr);

=head1 DESCRIPTION

Extends L<"DESCRIPTION" in Mail::Message::Field::Full|Mail::Message::Field::Full/"DESCRIPTION">.

=head1 OVERLOADED

Extends L<"OVERLOADED" in Mail::Message::Field::Full|Mail::Message::Field::Full/"OVERLOADED">.

=over 4

=item overload: B<""> stringification

Inherited, see L<Mail::Message::Field::Full/"OVERLOADED">

=item overload: B<'""'> stringification

Inherited, see L<Mail::Message::Field/"OVERLOADED">

=item overload: B<'0+'> numification

Inherited, see L<Mail::Message::Field/"OVERLOADED">

=item overload: B<'<=>'> numeric comparison

Inherited, see L<Mail::Message::Field/"OVERLOADED">

=item overload: B<bool> boolean

Inherited, see L<Mail::Message::Field/"OVERLOADED">

=item overload: B<cmp> string comparison

Inherited, see L<Mail::Message::Field/"OVERLOADED">

=back

=head1 METHODS

Extends L<"METHODS" in Mail::Message::Field::Full|Mail::Message::Field::Full/"METHODS">.

=head2 Constructors

Extends L<"Constructors" in Mail::Message::Field::Full|Mail::Message::Field::Full/"Constructors">.

=over 4

=item $obj-E<gt>B<clone>()

Inherited, see L<Mail::Message::Field/"Constructors">

=item $class-E<gt>B<from>($field, %options)

Inherited, see L<Mail::Message::Field::Full/"Constructors">

=item $class-E<gt>B<new>(($line | $name, $body, @attributes), %options)

=over 4

=item * B<new>(C<$line>)

Pass a C<$line> as it could be found in a file: a (possibly folded) line
which is terminated by a new-line.

=item * B<new>(C<$name>, C<$body>, C<@attributes>, C<%options>)

A set of values which shape the line.

=back

The C<$name> is a wellformed header name (you may use L<wellformedName()|Mail::Message::Field/"Attributes">) to
be sure about the casing.  The C<$body> is a string, one body object, or an
ARRAY of body objects.  In case of objects, they must fit to the
constructor of the field: the types which are accepted may differ.
The C<@attributes> LIST contains L<Mail::Message::Field::Attribute|Mail::Message::Field::Attribute>
objects.  Finally, there are some C<%options>.
Improves base, see L<Mail::Message::Field::Full/"METHODS">

 -Option    --Defined in                --Default
  attributes                              +[ ]
  charset     Mail::Message::Field::Full  undef
  datum                                   undef
  encoding    Mail::Message::Field::Full  'q'
  force       Mail::Message::Field::Full  false
  language    Mail::Message::Field::Full  undef

=over 2

=item attributes => \@attributes|\%attributes

There are various ways to specify these attributes: pass
an ARRAY which list of key-value pairs representing C<@attributes>,
or an HASH containing these pairs, or an ARRAY with
L<Mail::Message::Field::Attribute|Mail::Message::Field::Attribute> objects.

=item charset => $charset

=item datum => $date

The method name I<body> is very confusing, even in the RFC.  In MailBox,
for historical reasons, L<body()|Mail::Message::Field/"Attributes"> returns the part of the field contents
before the first semi-colon.  L<foldedBody()|Mail::Message::Field/"Attributes"> and L<unfoldedBody()|Mail::Message::Field/"Attributes">
address the whole field.

There is no common name for the piece of data before the parameters
(attributes) in the field-content mentioned in the RFCs, so let's call
it C<datum>.

=item encoding => 'q'|'Q'|'b'|'B'

=item force => BOOLEAN

=item language => $language

=back

» example: of a structured field

  my @attrs   = (Mail::Message::Field::Attribute->new(...), ...);
  my %options = (extra => 'the color blue');
  my $t = Mail::Message::Field::Full->new(To => \@addrs, @attrs, %options);

=back

=head2 Attributes

Extends L<"Attributes" in Mail::Message::Field::Full|Mail::Message::Field::Full/"Attributes">.

=over 4

=item $obj-E<gt>B<Name>()

Inherited, see L<Mail::Message::Field/"Attributes">

=item $obj-E<gt>B<body>()

Inherited, see L<Mail::Message::Field/"Attributes">

=item $obj-E<gt>B<folded>()

Inherited, see L<Mail::Message::Field/"Attributes">

=item $obj-E<gt>B<foldedBody>( [$body] )

Inherited, see L<Mail::Message::Field/"Attributes">

=item $obj-E<gt>B<name>()

Inherited, see L<Mail::Message::Field/"Attributes">

=item $obj-E<gt>B<unfoldedBody>( [$body, [$wrap]] )

Inherited, see L<Mail::Message::Field/"Attributes">

=item $obj-E<gt>B<wellformedName>( [STRING] )

Inherited, see L<Mail::Message::Field/"Attributes">

=back

=head2 The field

Extends L<"The field" in Mail::Message::Field::Full|Mail::Message::Field::Full/"The field">.

=over 4

=item $any-E<gt>B<isStructured>( [$name] )

Inherited, see L<Mail::Message::Field/"The field">

=item $obj-E<gt>B<length>()

Inherited, see L<Mail::Message::Field/"The field">

=item $obj-E<gt>B<nrLines>()

Inherited, see L<Mail::Message::Field/"The field">

=item $obj-E<gt>B<print>( [$fh] )

Inherited, see L<Mail::Message::Field/"The field">

=item $obj-E<gt>B<size>()

Inherited, see L<Mail::Message::Field/"The field">

=item $obj-E<gt>B<string>( [$wrap] )

Inherited, see L<Mail::Message::Field/"The field">

=item $obj-E<gt>B<toDisclose>()

Inherited, see L<Mail::Message::Field/"The field">

=back

=head2 Access to the body

Extends L<"Access to the body" in Mail::Message::Field::Full|Mail::Message::Field::Full/"Access to the body">.

=over 4

=item $obj-E<gt>B<decodedBody>(%options)

Inherited, see L<Mail::Message::Field::Full/"Access to the body">

=back

=head2 Access to the content

Extends L<"Access to the content" in Mail::Message::Field::Full|Mail::Message::Field::Full/"Access to the content">.

=over 4

=item $obj-E<gt>B<addresses>()

Inherited, see L<Mail::Message::Field/"Access to the content">

=item $obj-E<gt>B<attrPairs>()

Returns a list with attribute name and value pairs.

=item $obj-E<gt>B<attribute>( $object|<STRING, %options>|<$name,$value,%options> )

Add an attribute to the field.  The attributes are added left-to-right into
the string representation of the field, although the order of the attributes
is un-important, according to the RFCs.

You may pass a fully prepared L<Mail::Message::Field::Attribute|Mail::Message::Field::Attribute> C<$object>,
if you like to do all preparations for correct representation of the
data yourself.  You may also pass one C<STRING>, which is a fully prepared
attribute.  This C<STRING> will not be changed, so be careful about quoting
and encodings.

As third possibility, you can specify an attribute C<$name> and its C<$value>.
An attribute object will be created for you implicitly in both
cases where such object is not supplied, passing the C<%options>.  See
L<Mail::Message::Field::Attribute::new()|Mail::Message::Field::Attribute/"Constructors"> about the available C<%options>.

The attribute object is returned, however, when continuations are used this
may be an object you already know about.  C<undef> is returned when
construction fails (when the attribute is incorrect).
Improves base, see L<Mail::Message::Field/"Access to the content">

» example: 

  $f->attribute(filename => 'passwd');
  $f->attribute(filename => 'passwd', use_continuations => 0);

  my $attr = Mail::Message::Field::Attribute->new(...);
  $f->attribute($attr);

=item $obj-E<gt>B<attributes>()

Returns a list with all attributes, which are all
L<Mail::Message::Field::Attribute|Mail::Message::Field::Attribute> objects.  The attributes are not
ordered in any way.  The list may be empty.  Double attributes or
continuations are folded into one.
Improves base, see L<Mail::Message::Field/"Access to the content">

=item $obj-E<gt>B<beautify>()

Inherited, see L<Mail::Message::Field::Full/"Access to the content">

=item $obj-E<gt>B<comment>( [STRING] )

Inherited, see L<Mail::Message::Field/"Access to the content">

=item $any-E<gt>B<createComment>(STRING, %options)

Inherited, see L<Mail::Message::Field::Full/"Access to the content">

=item $any-E<gt>B<createPhrase>(STRING, %options)

Inherited, see L<Mail::Message::Field::Full/"Access to the content">

=item $any-E<gt>B<dateToTimestamp>(STRING)

Inherited, see L<Mail::Message::Field/"Access to the content">

=item $any-E<gt>B<stripCFWS>( [STRING] )

Inherited, see L<Mail::Message::Field/"Access to the content">

=item $obj-E<gt>B<study>()

Inherited, see L<Mail::Message::Field/"Access to the content">

=item $any-E<gt>B<toDate>( [$time] )

Inherited, see L<Mail::Message::Field/"Access to the content">

=item $obj-E<gt>B<toInt>()

Inherited, see L<Mail::Message::Field/"Access to the content">

=back

=head2 Internals

Extends L<"Internals" in Mail::Message::Field::Full|Mail::Message::Field::Full/"Internals">.

=over 4

=item $any-E<gt>B<decode>(STRING, %options)

Inherited, see L<Mail::Message::Field::Full/"Internals">

=item $obj-E<gt>B<encode>(STRING, %options)

Inherited, see L<Mail::Message::Field::Full/"Internals">

=back

=head2 Parsing

Extends L<"Parsing" in Mail::Message::Field::Full|Mail::Message::Field::Full/"Parsing">.

=over 4

=item $obj-E<gt>B<consume>( $line | <$name,<$body|$objects>> )

Inherited, see L<Mail::Message::Field/"Parsing">

=item $any-E<gt>B<consumeComment>(STRING)

Inherited, see L<Mail::Message::Field::Full/"Parsing">

=item $obj-E<gt>B<consumeDotAtom>(STRING)

Inherited, see L<Mail::Message::Field::Full/"Parsing">

=item $any-E<gt>B<consumePhrase>(STRING)

Inherited, see L<Mail::Message::Field::Full/"Parsing">

=item $obj-E<gt>B<datum>( [$value] )

The part of the field before the semi-colon (C<;>).

=item $obj-E<gt>B<defaultWrapLength>( [$length] )

Inherited, see L<Mail::Message::Field/"Parsing">

=item $any-E<gt>B<fold>( $name, $body, [$maxchars] )

Inherited, see L<Mail::Message::Field/"Parsing">

=item $obj-E<gt>B<parse>(STRING)

Inherited, see L<Mail::Message::Field::Full/"Parsing">

=item $obj-E<gt>B<produceBody>()

Inherited, see L<Mail::Message::Field::Full/"Parsing">

=item $obj-E<gt>B<setWrapLength>( [$length] )

Inherited, see L<Mail::Message::Field/"Parsing">

=item $obj-E<gt>B<stringifyData>(STRING|ARRAY|$objects)

Inherited, see L<Mail::Message::Field/"Parsing">

=item $obj-E<gt>B<unfold>(STRING)

Inherited, see L<Mail::Message::Field/"Parsing">

=back

=head2 Error handling

Extends L<"Error handling" in Mail::Message::Field::Full|Mail::Message::Field::Full/"Error handling">.

=over 4

=item $obj-E<gt>B<AUTOLOAD>()

Inherited, see L<Mail::Reporter/"Error handling">

=item $obj-E<gt>B<notImplemented>()

Inherited, see L<Mail::Reporter/"Error handling">

=back

=head2 Cleanup

Extends L<"Cleanup" in Mail::Message::Field::Full|Mail::Message::Field::Full/"Cleanup">.

=over 4

=item $obj-E<gt>B<DESTROY>()

Inherited, see L<Mail::Reporter/"Cleanup">

=back

=head1 DETAILS

Extends L<"DETAILS" in Mail::Message::Field::Full|Mail::Message::Field::Full/"DETAILS">.

=head1 DIAGNOSTICS

=over 4

=item Error: class $package does not implement method $method.

Fatal error: the specific C<$package> (or one of its superclasses) does not
implement this method where it should. This message means that some other
related classes do implement this method however the class at hand does
not.  Probably you should investigate this and probably inform the author
of the package.
Cast by C<notImplemented()>

=item Warning: field content is not numerical: $content

The numeric value of a field is requested (for instance the C<Lines> or
C<Content-Length> fields should be numerical), however the data contains
weird characters.
Cast by C<toInt()>

=item Error: field name too long (max $count), in '$name'.

It is not specified in the RFCs how long a field name can be, but
at least it should be a few characters shorter than the line wrap.
Cast by C<fold()>

=item Warning: illegal character in charset '$name'.

The field is created with an utf8 string which only contains data from the
specified character set.  However, that character set can never be a valid
name because it contains characters which are not permitted.
Cast by C<encode()>

=item Warning: illegal character in field name $name.

A new field is being created which does contain characters not permitted
by the RFCs.  Using this field in messages may break other e-mail clients
or transfer agents, and therefore mutulate or extinguish your message.
Cast by C<consume()>

=item Warning: illegal character in language '$name'.

The field is created with data which is specified to be in a certain language,
however, the name of the language cannot be valid: it contains characters
which are not permitted by the RFCs.
Cast by C<encode()>

=item Warning: illegal encoding '$name', using 'q'.

The RFCs only permit base64 (C<b > or C<B >) or quoted-printable
(C<q> or C<Q>) encoding.  Other than these four options are illegal.
Cast by C<encode()>

=back

=head1 SEE ALSO

This module is part of Mail-Message version 4.05,
built on April 10, 2026. Website: F<http://perl.overmeer.net/mailbox/>

=head1 LICENSE

For contributors see file ChangeLog.

This software is copyright (c) 2001-2026 by Mark Overmeer.

This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.

