Used to specify the address (URI) of the document from which the
requested resource address was obtained.

The "Free On-line Dictionary of Computing" as this to say about the
word I<referer>:

     <World-Wide Web> A misspelling of "referrer" which
     somehow made it into the {HTTP} standard.  A given {web
     page}'s referer (sic) is the {URL} of whatever web page
     contains the link that the user followed to the current
     page.  Most browsers pass this information as part of a
     request.

     (1998-10-19)

By popular demand C<referrer> exists as an alias for this method so you
can avoid this misspelling in your programs and still send the right
thing on the wire.

When setting the referrer, this method removes the fragment from the
given URI if it is present, as mandated by RFC2616.  Note that
the removal does I<not> happen automatically if using the header(),
push_header() or init_header() methods to set the referrer.

=item $h->www_authenticate

This header must be included as part of a C<401 Unauthorized> response.
The field value consist of a challenge that indicates the
authentication scheme and parameters applicable to the requested URI.

=item $h->proxy_authenticate

This header must be included in a C<407 Proxy Authentication Required>
response.

=item $h->authorization

=item $h->proxy_authorization

A user agent that wishes to authenticate itself with a server or a
proxy, may do so by including these headers.

=item $h->authorization_basic

This method is used to get or set an authorization header that use the
"Basic Authentication Scheme".  In array context it will return two
values; the user name and the password.  In scalar context it will
return I<"uname:password"> as a single string value.

When used to set the header value, it expects two arguments.  I<E.g.>:

  $h->authorization_basic($uname, $password);

The method will croak if the $uname contains a colon ':'.

=item $h->proxy_authorization_basic

Same as authorization_basic() but will set the "Proxy-Authorization"
header instead.

=back

=head1 NON-CANONICALIZED FIELD NAMES

The header field name spelling is normally canonicalized including the
'_' to '-' translation.  There are some application where this is not
appropriate.  Prefixing field names with ':' allow you to force a
specific spelling.  For example if you really want a header field name
to show up as C<foo_bar> instead of "Foo-Bar", you might set it like
this:

  $h->header(":foo_bar" => 1);

These field names are returned with the ':' intact for
$h->header_field_names and the $h->scan callback, but the colons do
not show in $h->as_string.

=head1 COPYRIGHT

Copyright 1995-2005 Gisle Aas.

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