3 package Catalyst::Plugin::Session;
6 with 'MooseX::Emulate::Class::Accessor::Fast';
8 use Catalyst::Exception ();
11 use Object::Signature ();
13 use List::Util qw/ max /;
15 use namespace::clean -except => 'meta';
17 our $VERSION = '0.39';
18 $VERSION = eval $VERSION;
20 my @session_data_accessors; # used in delete_session
22 __PACKAGE__->mk_accessors(
23 "_session_delete_reason",
24 @session_data_accessors = qw/
28 _extended_session_expires
33 _tried_loading_session_id
34 _tried_loading_session_data
35 _tried_loading_session_expires
36 _tried_loading_flash_data
40 sub _session_plugin_config {
42 # FIXME - Start warning once all the state/store modules have also been updated.
43 #$c->log->warn("Deprecated 'session' config key used, please use the key 'Plugin::Session' instead")
44 # if exists $c->config->{session}
45 #$c->config->{'Plugin::Session'} ||= delete($c->config->{session}) || {};
46 $c->config->{'Plugin::Session'} ||= $c->config->{session} || {};
52 $c->maybe::next::method(@_);
54 $c->check_session_plugin_requirements;
60 sub check_session_plugin_requirements {
63 unless ( $c->isa("Catalyst::Plugin::Session::State")
64 && $c->isa("Catalyst::Plugin::Session::Store") )
67 ( "The Session plugin requires both Session::State "
68 . "and Session::Store plugins to be used as well." );
71 Catalyst::Exception->throw($err);
78 my $cfg = $c->_session_plugin_config;
83 verify_user_agent => 0,
84 expiry_threshold => 0,
88 $c->maybe::next::method();
94 $c->maybe::next::method(@_);
96 if ( $c->_session_plugin_config->{flash_to_stash}
98 and my $flash_data = $c->flash )
100 @{ $c->stash }{ keys %$flash_data } = values %$flash_data;
104 sub finalize_headers {
107 # fix cookie before we send headers
108 $c->_save_session_expires;
110 # Force extension of session_expires before finalizing headers, so a pos
111 # up to date. First call to session_expires will extend the expiry, subs
112 # just return the previously extended value.
115 return $c->maybe::next::method(@_);
121 # We have to finalize our session *before* $c->engine->finalize_xxx is called,
122 # because we do not want to send the HTTP response before the session is stored/committed to
123 # the session database (or whatever Session::Store you use).
124 $c->finalize_session;
126 return $c->maybe::next::method(@_);
129 sub finalize_session {
132 $c->maybe::next::method(@_);
134 $c->_save_session_id;
138 $c->_clear_session_instance_data;
141 sub _session_updated {
144 if ( my $session_data = $c->_session ) {
146 no warnings 'uninitialized';
147 if ( Object::Signature::signature($session_data) ne
148 $c->_session_data_sig )
150 return $session_data;
162 sub _save_session_id {
165 # we already called set when allocating
166 # no need to tell the state plugins anything new
169 sub _save_session_expires {
172 if ( defined($c->_session_expires) ) {
174 if (my $sid = $c->sessionid) {
176 my $current = $c->_get_stored_session_expires;
177 my $extended = $c->session_expires;
178 if ($extended > $current) {
179 $c->store_session_data( "expires:$sid" => $extended );
189 if ( my $session_data = $c->_session_updated ) {
191 $session_data->{__updated} = time();
192 my $sid = $c->sessionid;
193 $c->store_session_data( "session:$sid" => $session_data );
195 $c->_session_data_sig(Object::Signature::signature($session_data));
203 if ( my $flash_data = $c->_flash ) {
205 my $hashes = $c->_flash_key_hashes || {};
206 my $keep = $c->_flash_keep_keys || {};
207 foreach my $key ( keys %$hashes ) {
208 if ( !exists $keep->{$key} and Object::Signature::signature( \$flash_data->{$key} ) eq $hashes->{$key} ) {
209 delete $flash_data->{$key};
213 my $sid = $c->sessionid;
215 my $session_data = $c->_session;
217 $session_data->{__flash} = $flash_data;
220 delete $session_data->{__flash};
222 $c->_session($session_data);
227 sub _load_session_expires {
229 return $c->_session_expires if $c->_tried_loading_session_expires;
230 $c->_tried_loading_session_expires(1);
232 if ( my $sid = $c->sessionid ) {
233 my $expires = $c->_get_stored_session_expires;
235 if ( $expires >= time() ) {
236 $c->_session_expires( $expires );
239 $c->delete_session( "session expired" );
249 return $c->_session if $c->_tried_loading_session_data;
250 $c->_tried_loading_session_data(1);
252 if ( my $sid = $c->sessionid ) {
253 if ( $c->_load_session_expires ) { # > 0
255 my $session_data = $c->get_session_data("session:$sid") || return;
256 $c->_session($session_data);
258 no warnings 'uninitialized'; # ne __address
259 if ( $c->_session_plugin_config->{verify_address}
260 && exists $session_data->{__address}
261 && $session_data->{__address} ne $c->request->address )
264 "Deleting session $sid due to address mismatch ("
265 . $session_data->{__address} . " != "
266 . $c->request->address . ")"
268 $c->delete_session("address mismatch");
271 if ( $c->_session_plugin_config->{verify_user_agent}
272 && $session_data->{__user_agent} ne $c->request->user_agent )
275 "Deleting session $sid due to user agent mismatch ("
276 . $session_data->{__user_agent} . " != "
277 . $c->request->user_agent . ")"
279 $c->delete_session("user agent mismatch");
283 $c->log->debug(qq/Restored session "$sid"/) if $c->debug;
284 $c->_session_data_sig( Object::Signature::signature($session_data) ) if $session_data;
285 $c->_expire_session_keys;
287 return $session_data;
296 return $c->_flash if $c->_tried_loading_flash_data;
297 $c->_tried_loading_flash_data(1);
299 if ( my $sid = $c->sessionid ) {
301 my $session_data = $c->session;
302 $c->_flash($session_data->{__flash});
304 if ( my $flash_data = $c->_flash )
306 $c->_flash_key_hashes({ map { $_ => Object::Signature::signature( \$flash_data->{$_} ) } keys %$flash_data });
315 sub _expire_session_keys {
316 my ( $c, $data ) = @_;
320 my $expire_times = ( $data || $c->_session || {} )->{__expire_keys} || {};
321 foreach my $key ( grep { $expire_times->{$_} < $now } keys %$expire_times ) {
322 delete $c->_session->{$key};
323 delete $expire_times->{$key};
327 sub _clear_session_instance_data {
329 $c->$_(undef) for @session_data_accessors;
330 $c->maybe::next::method(@_); # allow other plugins to hook in on this
333 sub change_session_id {
336 my $sessiondata = $c->session;
337 my $oldsid = $c->sessionid;
338 my $newsid = $c->create_session_id;
341 $c->log->debug(qq/change_sessid: deleting session data from "$oldsid"/) if $c->debug;
342 $c->delete_session_data("${_}:${oldsid}") for qw/session expires flash/;
345 $c->log->debug(qq/change_sessid: storing session data to "$newsid"/) if $c->debug;
346 $c->store_session_data( "session:$newsid" => $sessiondata );
352 my ( $c, $msg ) = @_;
354 $c->log->debug("Deleting session" . ( defined($msg) ? "($msg)" : '(no reason given)') ) if $c->debug;
356 # delete the session data
357 if ( my $sid = $c->sessionid ) {
358 $c->delete_session_data("${_}:${sid}") for qw/session expires flash/;
359 $c->delete_session_id($sid);
362 # reset the values in the context object
363 # see the BEGIN block
364 $c->_clear_session_instance_data;
366 $c->_session_delete_reason($msg);
369 sub session_delete_reason {
372 $c->session_is_valid; # check that it was loaded
374 $c->_session_delete_reason(@_);
377 sub session_expires {
380 if ( defined( my $expires = $c->_extended_session_expires ) ) {
382 } elsif ( defined( $expires = $c->_load_session_expires ) ) {
383 return $c->extend_session_expires( $expires );
389 sub extend_session_expires {
390 my ( $c, $expires ) = @_;
392 my $threshold = $c->_session_plugin_config->{expiry_threshold} || 0;
394 if ( my $sid = $c->sessionid ) {
395 my $expires = $c->_get_stored_session_expires;
396 my $cutoff = $expires - $threshold;
398 if (!$threshold || $cutoff <= time || $c->_session_updated) {
400 $c->_extended_session_expires( my $updated = $c->calculate_initial_session_expires() );
401 $c->extend_session_id( $sid, $updated );
419 sub change_session_expires {
420 my ( $c, $expires ) = @_;
423 my $sid = $c->sessionid;
424 my $time_exp = time() + $expires;
425 $c->store_session_data( "expires:$sid" => $time_exp );
428 sub _get_stored_session_expires {
431 if ( my $sid = $c->sessionid ) {
432 return $c->get_session_data("expires:$sid") || 0;
438 sub initial_session_expires {
440 return ( time() + $c->_session_plugin_config->{expires} );
443 sub calculate_initial_session_expires {
445 return max( $c->initial_session_expires, $c->_get_stored_session_expires );
448 sub calculate_extended_session_expires {
449 my ( $c, $prev ) = @_;
450 return ( time() + $prev );
453 sub reset_session_expires {
454 my ( $c, $sid ) = @_;
456 my $exp = $c->calculate_initial_session_expires;
457 $c->_session_expires( $exp );
459 # since we're setting _session_expires directly, make load_session_expires
460 # actually use that value.
462 $c->_tried_loading_session_expires(1);
463 $c->_extended_session_expires( $exp );
470 return $c->_sessionid || $c->_load_sessionid;
473 sub _load_sessionid {
475 return if $c->_tried_loading_session_id;
476 $c->_tried_loading_session_id(1);
478 if ( defined( my $sid = $c->get_session_id ) ) {
479 if ( $c->validate_session_id($sid) ) {
480 # temporarily set the inner key, so that validation will work
481 $c->_sessionid($sid);
484 my $err = "Tried to set invalid session ID '$sid'";
485 $c->log->error($err);
486 Catalyst::Exception->throw($err);
493 sub session_is_valid {
496 # force a check for expiry, but also __address, etc
497 if ( $c->_load_session ) {
504 sub validate_session_id {
505 my ( $c, $sid ) = @_;
507 $sid and $sid =~ /^[a-f\d]+$/i;
513 my $session = $c->_session || $c->_load_session || do {
514 $c->create_session_id_if_needed;
515 $c->initialize_session_data;
519 my $new_values = @_ > 1 ? { @_ } : $_[0];
520 croak('session takes a hash or hashref') unless ref $new_values;
522 for my $key (keys %$new_values) {
523 $session->{$key} = $new_values->{$key};
531 my ( $c, @keys ) = @_;
532 my $href = $c->_flash_keep_keys || $c->_flash_keep_keys({});
533 (@{$href}{@keys}) = ((undef) x @keys);
538 $c->_flash || $c->_load_flash || do {
539 $c->create_session_id_if_needed;
547 my $items = @_ > 1 ? {@_} : $_[0];
548 croak('flash takes a hash or hashref') unless ref $items;
549 @{ $c->_flash }{ keys %$items } = values %$items;
563 #$c->delete_session_data("flash:" . $c->sessionid); # should this be in here? or delayed till finalization?
564 $c->_flash_key_hashes({});
565 $c->_flash_keep_keys({});
569 sub session_expire_key {
570 my ( $c, %keys ) = @_;
573 @{ $c->session->{__expire_keys} }{ keys %keys } =
574 map { $now + $_ } values %keys;
577 sub initialize_session_data {
588 $c->_session_plugin_config->{verify_address}
589 ? ( __address => $c->request->address||'' )
593 $c->_session_plugin_config->{verify_user_agent}
594 ? ( __user_agent => $c->request->user_agent||'' )
601 sub generate_session_id {
604 my $digest = $c->_find_digest();
605 $digest->add( $c->session_hash_seed() );
606 return $digest->hexdigest;
609 sub create_session_id_if_needed {
611 $c->create_session_id unless $c->sessionid;
614 sub create_session_id {
617 my $sid = $c->generate_session_id;
619 $c->log->debug(qq/Created session "$sid"/) if $c->debug;
621 $c->_sessionid($sid);
622 $c->reset_session_expires;
623 $c->set_session_id($sid);
630 sub session_hash_seed {
633 return join( "", ++$counter, time, rand, $$, {}, overload::StrVal($c), );
638 sub _find_digest () {
640 foreach my $alg (qw/SHA-1 SHA-256 MD5/) {
641 if ( eval { Digest->new($alg) } ) {
646 Catalyst::Exception->throw(
647 "Could not find a suitable Digest module. Please install "
648 . "Digest::SHA1, Digest::SHA, or Digest::MD5" )
652 return Digest->new($usable);
659 $c->maybe::next::method(),
662 ? ( [ "Session ID" => $c->sessionid ], [ Session => $c->session ], )
668 sub get_session_id { shift->maybe::next::method(@_) }
669 sub set_session_id { shift->maybe::next::method(@_) }
670 sub delete_session_id { shift->maybe::next::method(@_) }
671 sub extend_session_id { shift->maybe::next::method(@_) }
681 Catalyst::Plugin::Session - Generic Session plugin - ties together server side storage and client side state required to maintain session data.
685 # To get sessions to "just work", all you need to do is use these plugins:
689 Session::Store::FastMmap
690 Session::State::Cookie
693 # you can replace Store::FastMmap with Store::File - both have sensible
694 # default configurations (see their docs for details)
696 # more complicated backends are available for other scenarios (DBI storage,
700 # after you've loaded the plugins you can save session data
701 # For example, if you are writing a shopping cart, it could be implemented
704 sub add_item : Local {
705 my ( $self, $c ) = @_;
707 my $item_id = $c->req->param("item");
709 # $c->session is a hash ref, a bit like $c->stash
710 # the difference is that it' preserved across requests
712 push @{ $c->session->{items} }, $item_id;
714 $c->forward("MyView");
717 sub display_items : Local {
718 my ( $self, $c ) = @_;
720 # values in $c->session are restored
721 $c->stash->{items_to_display} =
722 [ map { MyModel->retrieve($_) } @{ $c->session->{items} } ];
724 $c->forward("MyView");
729 The Session plugin is the base of two related parts of functionality required
730 for session management in web applications.
732 The first part, the State, is getting the browser to repeat back a session key,
733 so that the web application can identify the client and logically string
734 several requests together into a session.
736 The second part, the Store, deals with the actual storage of information about
737 the client. This data is stored so that the it may be revived for every request
738 made by the same client.
740 This plugin links the two pieces together.
742 =head1 RECOMENDED BACKENDS
746 =item Session::State::Cookie
748 The only really sane way to do state is using cookies.
750 =item Session::Store::File
752 A portable backend, based on Cache::File.
754 =item Session::Store::FastMmap
756 A fast and flexible backend, based on Cache::FastMmap.
766 An accessor for the session ID value.
770 Returns a hash reference that might contain unserialized values from previous
771 requests in the same session, and whose modified value will be saved for future
774 This method will automatically create a new session and session ID if none
777 You can also set session keys by passing a list of key/value pairs or a
780 $c->session->{foo} = "bar"; # This works.
781 $c->session(one => 1, two => 2); # And this.
782 $c->session({ answer => 42 }); # And this.
784 =item session_expires
786 This method returns the time when the current session will expire, or 0 if
787 there is no current session. If there is a session and it already expired, it
788 will delete the session and return 0 as well.
792 This is like Ruby on Rails' flash data structure. Think of it as a stash that
793 lasts for longer than one request, letting you redirect instead of forward.
795 The flash data will be cleaned up only on requests on which actually use
796 $c->flash (thus allowing multiple redirections), and the policy is to delete
797 all the keys which haven't changed since the flash data was loaded at the end
800 Note that use of the flash is an easy way to get data across requests, but
801 it's also strongly disrecommended, due it it being inherently plagued with
802 race conditions. This means that it's unlikely to work well if your
803 users have multiple tabs open at once, or if your site does a lot of AJAX
806 L<Catalyst::Plugin::StatusMessage> is the recommended alternative solution,
807 as this doesn't suffer from these issues.
810 my ( $self, $c ) = @_;
812 $c->flash->{beans} = 10;
813 $c->response->redirect( $c->uri_for("foo") );
817 my ( $self, $c ) = @_;
819 my $value = $c->flash->{beans};
823 $c->response->redirect( $c->uri_for("bar") );
827 my ( $self, $c ) = @_;
829 if ( exists $c->flash->{beans} ) { # false
836 Zap all the keys in the flash regardless of their current state.
838 =item keep_flash @keys
840 If you want to keep a flash key for the next request too, even if it hasn't
841 changed, call C<keep_flash> and pass in the keys as arguments.
843 =item delete_session REASON
845 This method is used to invalidate a session. It takes an optional parameter
846 which will be saved in C<session_delete_reason> if provided.
848 NOTE: This method will B<also> delete your flash data.
850 =item session_delete_reason
852 This accessor contains a string with the reason a session was deleted. Possible
867 =item session_expire_key $key, $ttl
869 Mark a key to expire at a certain time (only useful when shorter than the
870 expiry time for the whole session).
874 __PACKAGE__->config('Plugin::Session' => { expires => 10000000000 }); # "forever"
875 (NB If this number is too large, Y2K38 breakage could result.)
879 $c->session_expire_key( __user => 3600 );
881 Will make the session data survive, but the user will still be logged out after
884 Note that these values are not auto extended.
886 =item change_session_id
888 By calling this method you can force a session id change while keeping all
889 session data. This method might come handy when you are paranoid about some
890 advanced variations of session fixation attack.
892 If you want to prevent this session fixation scenario:
894 0) let us have WebApp with anonymous and authenticated parts
895 1) a hacker goes to vulnerable WebApp and gets a real sessionid,
896 just by browsing anonymous part of WebApp
897 2) the hacker inserts (somehow) this values into a cookie in victim's browser
898 3) after the victim logs into WebApp the hacker can enter his/her session
900 you should call change_session_id in your login controller like this:
902 if ($c->authenticate( { username => $user, password => $pass } )) {
904 $c->change_session_id;
911 =item change_session_expires $expires
913 You can change the session expiration time for this session;
915 $c->change_session_expires( 4000 );
917 Note that this only works to set the session longer than the config setting.
921 =head1 INTERNAL METHODS
927 This method is extended to also make calls to
928 C<check_session_plugin_requirements> and C<setup_session>.
930 =item check_session_plugin_requirements
932 This method ensures that a State and a Store plugin are also in use by the
937 This method populates C<< $c->config('Plugin::Session') >> with the default values
938 listed in L</CONFIGURATION>.
942 This method is extended.
944 Its only effect is if the (off by default) C<flash_to_stash> configuration
945 parameter is on - then it will copy the contents of the flash to the stash at
948 =item finalize_headers
950 This method is extended and will extend the expiry time before sending
955 This method is extended and will call finalize_session before the other
956 finalize_body methods run. Here we persist the session data if a session exists.
958 =item initialize_session_data
960 This method will initialize the internal structure of the session, and is
961 called by the C<session> method if appropriate.
963 =item create_session_id
965 Creates a new session ID using C<generate_session_id> if there is no session ID
968 =item validate_session_id SID
970 Make sure a session ID is of the right format.
972 This currently ensures that the session ID string is any amount of case
973 insensitive hexadecimal characters.
975 =item generate_session_id
977 This method will return a string that can be used as a session ID. It is
978 supposed to be a reasonably random string with enough bits to prevent
979 collision. It basically takes C<session_hash_seed> and hashes it using SHA-1,
980 MD5 or SHA-256, depending on the availability of these modules.
982 =item session_hash_seed
984 This method is actually rather internal to generate_session_id, but should be
985 overridable in case you want to provide more random data.
987 Currently it returns a concatenated string which contains:
993 =item * The current time
995 =item * One value from C<rand>.
997 =item * The stringified value of a newly allocated hash reference
999 =item * The stringified value of the Catalyst context object
1003 in the hopes that those combined values are entropic enough for most uses. If
1004 this is not the case you can replace C<session_hash_seed> with e.g.
1006 sub session_hash_seed {
1007 open my $fh, "<", "/dev/random";
1008 read $fh, my $bytes, 20;
1013 Or even more directly, replace C<generate_session_id>:
1015 sub generate_session_id {
1016 open my $fh, "<", "/dev/random";
1017 read $fh, my $bytes, 20;
1019 return unpack("H*", $bytes);
1022 Also have a look at L<Crypt::Random> and the various openssl bindings - these
1023 modules provide APIs for cryptographically secure random data.
1025 =item finalize_session
1027 Clean up the session during C<finalize>.
1029 This clears the various accessors after saving to the store.
1033 See L<Catalyst/dump_these> - ammends the session data structure to the list of
1034 dumped objects if session ID is defined.
1037 =item calculate_extended_session_expires
1039 =item calculate_initial_session_expires
1041 =item create_session_id_if_needed
1043 =item delete_session_id
1045 =item extend_session_expires
1047 Note: this is *not* used to give an individual user a longer session. See
1048 'change_session_expires'.
1050 =item extend_session_id
1052 =item get_session_id
1054 =item reset_session_expires
1056 =item session_is_valid
1058 =item set_session_id
1060 =item initial_session_expires
1064 =head1 USING SESSIONS DURING PREPARE
1066 The earliest point in time at which you may use the session data is after
1067 L<Catalyst::Plugin::Session>'s C<prepare_action> has finished.
1069 State plugins must set $c->session ID before C<prepare_action>, and during
1070 C<prepare_action> L<Catalyst::Plugin::Session> will actually load the data from
1073 sub prepare_action {
1076 # don't touch $c->session yet!
1078 $c->NEXT::prepare_action( @_ );
1080 $c->session; # this is OK
1081 $c->sessionid; # this is also OK
1084 =head1 CONFIGURATION
1086 $c->config('Plugin::Session' => {
1090 All configuation parameters are provided in a hash reference under the
1091 C<Plugin::Session> key in the configuration hash.
1097 The time-to-live of each session, expressed in seconds. Defaults to 7200 (two
1100 =item expiry_threshold
1102 Only update the session expiry time if it would otherwise expire
1103 within this many seconds from now.
1105 The purpose of this is to keep the session store from being updated
1106 when nothing else in the session is updated.
1108 Defaults to 0 (in which case, the expiration will always be updated).
1110 =item verify_address
1112 When true, C<< $c->request->address >> will be checked at prepare time. If it is
1113 not the same as the address that initiated the session, the session is deleted.
1117 =item verify_user_agent
1119 When true, C<< $c->request->user_agent >> will be checked at prepare time. If it
1120 is not the same as the user agent that initiated the session, the session is
1125 =item flash_to_stash
1127 This option makes it easier to have actions behave the same whether they were
1128 forwarded to or redirected to. On prepare time it copies the contents of
1129 C<flash> (if any) to the stash.
1135 The hash reference returned by C<< $c->session >> contains several keys which
1136 are automatically set:
1142 This key no longer exists. Use C<session_expires> instead.
1146 The last time a session was saved to the store.
1150 The time when the session was first created.
1154 The value of C<< $c->request->address >> at the time the session was created.
1155 This value is only populated if C<verify_address> is true in the configuration.
1159 The value of C<< $c->request->user_agent >> at the time the session was created.
1160 This value is only populated if C<verify_user_agent> is true in the configuration.
1166 =head2 Round the Robin Proxies
1168 C<verify_address> could make your site inaccessible to users who are behind
1169 load balanced proxies. Some ISPs may give a different IP to each request by the
1170 same client due to this type of proxying. If addresses are verified these
1171 users' sessions cannot persist.
1173 To let these users access your site you can either disable address verification
1174 as a whole, or provide a checkbox in the login dialog that tells the server
1175 that it's OK for the address of the client to change. When the server sees that
1176 this box is checked it should delete the C<__address> special key from the
1177 session hash when the hash is first created.
1179 =head2 Race Conditions
1181 In this day and age where cleaning detergents and Dutch football (not the
1182 American kind) teams roam the plains in great numbers, requests may happen
1183 simultaneously. This means that there is some risk of session data being
1184 overwritten, like this:
1190 request a starts, request b starts, with the same session ID
1194 session data is loaded in request a
1198 session data is loaded in request b
1202 session data is changed in request a
1206 request a finishes, session data is updated and written to store
1210 request b finishes, session data is updated and written to store, overwriting
1211 changes by request a
1215 For applications where any given user's session is only making one request
1216 at a time this plugin should be safe enough.
1224 Yuval Kogman, C<nothingmuch@woobling.org>
1228 Tomas Doran (t0m) C<bobtfish@bobtfish.net> (current maintainer)
1234 Florian Ragwitz (rafl) C<rafl@debian.org>
1236 Kent Fredric (kentnl)
1238 And countless other contributers from #catalyst. Thanks guys!
1242 Devin Austin (dhoss) <dhoss@cpan.org>
1244 Robert Rothenberg <rrwo@cpan.org> (on behalf of Foxtons Ltd.)
1246 =head1 COPYRIGHT & LICENSE
1248 Copyright (c) 2005 the aforementioned authors. All rights
1249 reserved. This program is free software; you can redistribute
1250 it and/or modify it under the same terms as Perl itself.