Text::Header - RFC 822/2068 header and unheader functions

   use Text::Header;     # header and unheader exported

   # Construct headers similar to CGI.pm and HTTP::Headers

   @HEADERS = header(content_type => 'text/html',
                     author => 'Nathan Wiger',
                     last_modified => $date,
                     accept => [qw(text/html text/plain)]);

   # The above produces the array:

   @HEADERS = ("Content-Type: text/html\n",
               "Author: Nathan Wiger\n",
               "Last-Modified: Wed Sep 27 13:31:06 PDT 2000\n",
               "Accept: text/html, text/plain\n");

   # Can also construct SMTP headers to format mail

   @mail_headers = header(from => 'Nathan Wiger <nate@sun.com>',
                          to => 'perl5-porters@perl.org');

   print $MAIL @mail_headers, "\nKeep up the great work!\n";

   # The above would print this to the $MAIL handle:

   From: Nathan Wiger <nate@sun.com>
   To: perl5-porters@perl.org

   Keep up the great work!

This module provides two new functions, header and unheader, which provide general-purpose RFC 822 header construction and parsing. They do not provide any intelligent defaults of HTTP-specific methods. They are simply aimed at providing an easy means to address the mechanics of header parsing.

The output style is designed to mimic CGI.pm and HTTP::Headers, so that users familiar with these interfaces will feel at home with these functions. As shown above, the headers function automatically does the following:

   1. uc's the first letter of each tag token and lc's the
      rest, also converting _'s to -'s automatically

   2. Adds a colon separating each tag and its value, and
      exactly one newline after each one

   3. Combines list elements into a comma-delimited
      string 

Note that a list is always joined into a comma-delimited string. To insert multiple separate headers, simply call header with multiple args:

   push @out, header(accept => 'text/html',
                     accept => 'text/plain');

This would create multiple "Accept:" lines.

Note that unlike CGI.pm, the header function provided here does not provide any intelligent defaults. If called as:

    @out_headers = header;

It will return an empty list. This allows header to be more general pupose, so it can provide SMTP and other headers as well. You can also use it as a generic text formatting tool, hence the reason it's under the Text:: hierarchy.

The unheader function works in exactly the opposite direction from header, pulling apart headers and returning a list. unheader:

   1. lc's the entire tag name, converting -'s to _'s

   2. Separates each tag based on the colon delimiter,
      chomping newlines.

   3. Returns a list of tag/value pairs for easy assignment
      to a hash

So, assuming the @HEADERS array shown up top:

   %myheaders = unheader(@HEADERS);

The hash %myheaders would have the following values:

   %myheaders = (
       content_type => 'text/html',
       author => 'Nathan Wiger',
       last_modified => 'Wed Sep 27 13:31:06 PDT 2000',
       accept => 'text/html, text/plain'
   );

Note that all keys are converted to lowercase, and their values have their newlines stripped. However, note that comma-separated fields are not split up on input. This cannot be done reliably because some fields, such as the HTTP Date: header, can contain commas even though they are not lists. Inferring this type of structure would require knowledge of content, and these functions are specifically designed to be content-independent.

The unheader function will respect line wrapping, as seen in SMTP headers. It will simply join the lines and return the value, so that:

   %mail = unheader("To: Nathan Wiger <nate@sun.com>,
                             perl5-porters@perl.org");

Would return:

   $mail{to} = "Nathan Wiger <nate@sun.com>, perl5-porters@perl.org"

Notice that multiple spaces between the comma separator have been condensed to a single space. Since the header and unheader functions are direct inverses, this call:

   @out = header unheader @in;

Will result in @out being exactly equivalent to @in.

This is designed as both a Perl 5 module and also a Perl 6 prototype. Please see the Perl 6 proposal at http://dev.perl.org/rfc/333.html

This module is designed to be fully compliant with the internet standards RFC 822 (SMTP Headers) and RFC 2068 (HTTP Headers).

Copyright (c) 2000 Nathan Wiger <nate@sun.com>. All Rights Reserved.

This module is free software; you may copy this under the terms of the GNU General Public License, or the Artistic License, copies of which should have accompanied your Perl kit.