NAME

       Mail::Header - manipulate MIME headers

SYNOPSIS

        use Mail::Header;

        my $head = Mail::Header->new;
        my $head = Mail::Header->new( \*STDIN );
        my $head = Mail::Header->new( [<>], Modify => 0);

DESCRIPTION

       Read, write, create, and manipulate MIME headers, the leading part of each modern e-mail
       message, but also used in other protocols like HTTP.  The fields are kept in Mail::Field
       objects.

       Be aware that the header fields each have a name part, which shall be treated case-
       insensitive, and a content part, which may be folded over multiple lines.

       Mail::Header does not always follow the RFCs strict enough, does not help you with
       character encodings.  It does not use weak references where it could (because those did
       not exist when the module was written) which costs some performance and make the
       implementation a little more complicated.  The Mail::Message::Head implementation is much
       newer and therefore better.

METHODS

   Constructors
       $obj->dup()
           Create a duplicate of the current object.

       $obj->new([ARG], [OPTIONS])
       Mail::Header->new([ARG], [OPTIONS])
           ARG may be either a file descriptor (reference to a GLOB) or a reference to an array.
           If given the new object will be initialized with headers either from the array of read
           from the file descriptor.

           OPTIONS is a list of options given in the form of key-value pairs, just like a hash
           table. Valid options are

            -Option    --Default
             FoldLength  79
             MailFrom    'KEEP'
             Modify      false

           FoldLength => INTEGER
             The default length of line to be used when folding header lines.  See fold_length().

           MailFrom => 'IGNORE'|'COERCE'|'KEEP'|'ERROR'
             See method mail_from().

           Modify => BOOLEAN
             If this value is true then the headers will be re-formatted, otherwise the format of
             the header lines will remain unchanged.

   "Fake" constructors
       Be warned that the next constructors all require an already created header object, of
       which the original content will be destroyed.

       $obj->empty()
           Empty an existing "Mail::Header" object of all lines.

       $obj->extract(ARRAY)
           Extract a header from the given array into an existing Mail::Header object. "extract"
           will modify this array.  Returns the object that the method was called on.

       $obj->header([ARRAY])
           "header" does multiple operations. First it will extract a header from the ARRAY, if
           given. It will then reformat the header (if reformatting is permitted), and finally
           return a reference to an array which contains the header in a printable form.

       $obj->header_hashref([HASH])
           As header(), but it will eventually set headers from a hash reference, and it will
           return the headers as a hash reference.

           example:

            $fields->{From} = 'Tobias Brox <tobix@cpan.org>';
            $fields->{To}   = ['you@somewhere', 'me@localhost'];
            $head->header_hashref($fields);

       $obj->read(FILEHANDLE)
           Read a header from the given file descriptor into an existing Mail::Header object.

   Accessors
       $obj->fold_length([TAG], [LENGTH])
           Set the default fold length for all tags or just one. With no arguments the default
           fold length is returned. With two arguments it sets the fold length for the given tag
           and returns the previous value. If only "LENGTH" is given it sets the default fold
           length for the current object.

           In the two argument form "fold_length" may be called as a static method, setting
           default fold lengths for tags that will be used by all "Mail::Header" objects. See the
           "fold" method for a description on how "Mail::Header" uses these values.

       $obj->mail_from('IGNORE'|'COERCE'|'KEEP'|'ERROR')
           This specifies what to do when a `From ' line is encountered.  Valid values are
           "IGNORE" - ignore and discard the header, "ERROR" - invoke an error (call die),
           "COERCE" - rename them as Mail-From and "KEEP" - keep them.

       $obj->modify([VALUE])
           If "VALUE" is false then "Mail::Header" will not do any automatic reformatting of the
           headers, other than to ensure that the line starts with the tags given.

   Processing
       $obj->add(TAG, LINE [, INDEX])
           Add a new line to the header. If TAG is "undef" the the tag will be extracted from the
           beginning of the given line. If INDEX is given, the new line will be inserted into the
           header at the given point, otherwise the new line will be appended to the end of the
           header.

       $obj->as_string()
           Returns the header as a single string.

       $obj->cleanup()
           Remove any header line that, other than the tag, only contains whitespace

       $obj->combine(TAG [, WITH])
           Combine all instances of TAG into one. The lines will be joined together WITH, or a
           single space if not given. The new item will be positioned in the header where the
           first instance was, all other instances of TAG will be removed.

       $obj->count(TAG)
           Returns the number of times the given atg appears in the header

       $obj->delete(TAG [, INDEX ])
           Delete a tag from the header. If an INDEX id is given, then the Nth instance of the
           tag will be removed. If no INDEX is given, then all instances of tag will be removed.

       $obj->fold([LENGTH])
           Fold the header. If LENGTH is not given, then "Mail::Header" uses the following rules
           to determine what length to fold a line.

       $obj->get(TAG [, INDEX])
           Get the text from a line. If an INDEX is given, then the text of the Nth instance will
           be returned. If it is not given the return value depends on the context in which "get"
           was called. In an array context a list of all the text from all the instances of the
           TAG will be returned. In a scalar context the text for the first instance will be
           returned.

           The lines are unfolded, but still terminated with a new-line (see "chomp")

       $obj->print([FILEHANDLE])
           Print the header to the given file descriptor, or "STDOUT" if no file descriptor is
           given.

       $obj->replace(TAG, LINE [, INDEX ])
           Replace a line in the header.  If TAG is "undef" the the tag will be extracted from
           the beginning of the given line. If INDEX is given the new line will replace the Nth
           instance of that tag, otherwise the first instance of the tag is replaced. If the tag
           does not appear in the header then a new line will be appended to the header.

       $obj->tags()
           Returns an array of all the tags that exist in the header. Each tag will only appear
           in the list once. The order of the tags is not specified.

       $obj->unfold([TAG])
           Unfold all instances of the given tag so that they do not spread across multiple
           lines. If "TAG" is not given then all lines are unfolded.

           The unfolding process is wrong but (for compatibility reasons) will not be repaired:
           only one blank at the start of the line should be removed, not all of them.

SEE ALSO

       This module is part of the MailTools distribution, http://perl.overmeer.net/mailtools/.

AUTHORS

       The MailTools bundle was developed by Graham Barr.  Later, Mark Overmeer took over
       maintenance without commitment to further development.

       Mail::Cap by Gisle Aas <aas@oslonett.no>.  Mail::Field::AddrList by Peter Orbaek
       <poe@cit.dk>.  Mail::Mailer and Mail::Send by Tim Bunce <Tim.Bunce@ig.co.uk>.  For other
       contributors see ChangeLog.

LICENSE

       Copyrights 1995-2000 Graham Barr <gbarr@pobox.com> and 2001-2007 Mark Overmeer
       <perl@overmeer.net>.

       This program is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.  See http://www.perl.com/perl/misc/Artistic.html