1 ;# $Id: Storable.pm,v 1.0.1.13 2001/12/01 13:34:49 ram Exp $
3 ;# Copyright (c) 1995-2000, Raphael Manfredi
5 ;# You may redistribute only under the same terms as Perl 5, as specified
6 ;# in the README file that comes with the distribution.
8 ;# $Log: Storable.pm,v $
9 ;# Revision 1.0.1.13 2001/12/01 13:34:49 ram
10 ;# patch14: avoid requiring Fcntl upfront, useful to embedded runtimes
11 ;# patch14: store_fd() will now correctly autoflush file if needed
13 ;# Revision 1.0.1.12 2001/08/28 21:51:51 ram
14 ;# patch13: fixed truncation race with lock_retrieve() in lock_store()
16 ;# Revision 1.0.1.11 2001/07/01 11:22:14 ram
17 ;# patch12: systematically use "=over 4" for POD linters
18 ;# patch12: updated version number
20 ;# Revision 1.0.1.10 2001/03/15 00:20:25 ram
21 ;# patch11: updated version number
23 ;# Revision 1.0.1.9 2001/02/17 12:37:32 ram
24 ;# patch10: forgot to increase version number at previous patch
26 ;# Revision 1.0.1.8 2001/02/17 12:24:37 ram
27 ;# patch8: fixed incorrect error message
29 ;# Revision 1.0.1.7 2001/01/03 09:39:02 ram
30 ;# patch7: added CAN_FLOCK to determine whether we can flock() or not
32 ;# Revision 1.0.1.6 2000/11/05 17:20:25 ram
33 ;# patch6: increased version number
35 ;# Revision 1.0.1.5 2000/10/26 17:10:18 ram
36 ;# patch5: documented that store() and retrieve() can return undef
37 ;# patch5: added paragraph explaining the auto require for thaw hooks
39 ;# Revision 1.0.1.4 2000/10/23 18:02:57 ram
40 ;# patch4: protected calls to flock() for dos platform
41 ;# patch4: added logcarp emulation if they don't have Log::Agent
43 ;# Revision 1.0.1.3 2000/09/29 19:49:01 ram
44 ;# patch3: updated version number
46 ;# Revision 1.0.1.2 2000/09/28 21:42:51 ram
47 ;# patch2: added lock_store lock_nstore lock_retrieve
49 ;# Revision 1.0.1.1 2000/09/17 16:46:21 ram
50 ;# patch1: documented that doubles are stringified by nstore()
51 ;# patch1: added Salvador Ortiz Garcia in CREDITS section
53 ;# Revision 1.0 2000/09/01 19:40:41 ram
54 ;# Baseline for first official release.
59 package Storable; @ISA = qw(Exporter DynaLoader);
61 @EXPORT = qw(store retrieve);
63 nstore store_fd nstore_fd fd_retrieve
67 lock_store lock_nstore lock_retrieve
71 use vars qw($forgive_me $VERSION);
74 *AUTOLOAD = \&AutoLoader::AUTOLOAD; # Grrr...
77 # Use of Log::Agent is optional
80 eval "use Log::Agent";
82 unless (defined @Log::Agent::EXPORT) {
96 # They might miss :flock in Fcntl
100 if (eval { require Fcntl; 1 } && exists $Fcntl::EXPORT_TAGS{'flock'}) {
101 Fcntl->import(':flock');
113 sub retrieve_fd { &fd_retrieve } # Backward compatibility
116 # Determine whether locking is possible, but only when needed.
122 return $CAN_FLOCK if defined $CAN_FLOCK;
123 require Config; import Config;
125 $Config{'d_flock'} ||
126 $Config{'d_fcntl_can_lock'} ||
130 sub show_file_magic {
133 # To recognize the data files of the Perl module Storable,
134 # the following lines need to be added to the local magic(5) file,
135 # usually either /usr/share/misc/magic or /etc/magic.
137 0 string perl-store perl Storable(v0.6) data
138 >4 byte >0 (net-order %d)
139 >>4 byte &01 (network-ordered)
140 >>4 byte =3 (major 1)
141 >>4 byte =2 (major 1)
143 0 string pst0 perl Storable(v0.7) data
145 >>4 byte &01 (network-ordered)
146 >>4 byte =5 (major 2)
147 >>4 byte =4 (major 2)
148 >>5 byte >0 (minor %d)
159 # Store target object hierarchy, identified by a reference to its root.
160 # The stored object tree may later be retrieved to memory via retrieve.
161 # Returns undef if an I/O error occurred, in which case the file is
165 return _store(\&pstore, @_, 0);
171 # Same as store, but in network order.
174 return _store(\&net_pstore, @_, 0);
180 # Same as store, but flock the file first (advisory locking).
183 return _store(\&pstore, @_, 1);
189 # Same as nstore, but flock the file first (advisory locking).
192 return _store(\&net_pstore, @_, 1);
195 # Internal store to file routine
199 my ($file, $use_locking) = @_;
200 logcroak "not a reference" unless ref($self);
201 logcroak "wrong argument number" unless @_ == 2; # No @foo in arglist
204 open(FILE, ">>$file") || logcroak "can't write into $file: $!";
205 unless (&CAN_FLOCK) {
206 logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O";
209 flock(FILE, LOCK_EX) ||
210 logcroak "can't get exclusive lock on $file: $!";
212 # Unlocking will happen when FILE is closed
214 open(FILE, ">$file") || logcroak "can't create $file: $!";
216 binmode FILE; # Archaic systems...
217 my $da = $@; # Don't mess if called from exception handler
219 # Call C routine nstore or pstore, depending on network order
220 eval { $ret = &$xsptr(*FILE, $self) };
221 close(FILE) or $ret = undef;
222 unlink($file) or warn "Can't unlink $file: $!\n" if $@ || !defined $ret;
223 logcroak $@ if $@ =~ s/\.?\n$/,/;
225 return $ret ? $ret : undef;
231 # Same as store, but perform on an already opened file descriptor instead.
232 # Returns undef if an I/O error occurred.
235 return _store_fd(\&pstore, @_);
241 # Same as store_fd, but in network order.
244 my ($self, $file) = @_;
245 return _store_fd(\&net_pstore, @_);
248 # Internal store routine on opened file descriptor
253 logcroak "not a reference" unless ref($self);
254 logcroak "too many arguments" unless @_ == 1; # No @foo in arglist
255 my $fd = fileno($file);
256 logcroak "not a valid file descriptor" unless defined $fd;
257 my $da = $@; # Don't mess if called from exception handler
259 # Call C routine nstore or pstore, depending on network order
260 eval { $ret = &$xsptr($file, $self) };
261 logcroak $@ if $@ =~ s/\.?\n$/,/;
262 local $\; print $file ''; # Autoflush the file if wanted
264 return $ret ? $ret : undef;
270 # Store oject and its hierarchy in memory and return a scalar
271 # containing the result.
274 _freeze(\&mstore, @_);
280 # Same as freeze but in network order.
283 _freeze(\&net_mstore, @_);
286 # Internal freeze routine
290 logcroak "not a reference" unless ref($self);
291 logcroak "too many arguments" unless @_ == 0; # No @foo in arglist
292 my $da = $@; # Don't mess if called from exception handler
294 # Call C routine mstore or net_mstore, depending on network order
295 eval { $ret = &$xsptr($self) };
296 logcroak $@ if $@ =~ s/\.?\n$/,/;
298 return $ret ? $ret : undef;
304 # Retrieve object hierarchy from disk, returning a reference to the root
305 # object of that tree.
314 # Same as retrieve, but with advisory locking.
320 # Internal retrieve routine
322 my ($file, $use_locking) = @_;
324 open(FILE, $file) || logcroak "can't open $file: $!";
325 binmode FILE; # Archaic systems...
327 my $da = $@; # Could be from exception handler
329 unless (&CAN_FLOCK) {
330 logcarp "Storable::lock_store: fcntl/flock emulation broken on $^O";
333 flock(FILE, LOCK_SH) || logcroak "can't get shared lock on $file: $!";
334 # Unlocking will happen when FILE is closed
336 eval { $self = pretrieve(*FILE) }; # Call C routine
338 logcroak $@ if $@ =~ s/\.?\n$/,/;
346 # Same as retrieve, but perform from an already opened file descriptor instead.
350 my $fd = fileno($file);
351 logcroak "not a valid file descriptor" unless defined $fd;
353 my $da = $@; # Could be from exception handler
354 eval { $self = pretrieve($file) }; # Call C routine
355 logcroak $@ if $@ =~ s/\.?\n$/,/;
363 # Recreate objects in memory from an existing frozen image created
364 # by freeze. If the frozen image passed is undef, return undef.
368 return undef unless defined $frozen;
370 my $da = $@; # Could be from exception handler
371 eval { $self = mretrieve($frozen) }; # Call C routine
372 logcroak $@ if $@ =~ s/\.?\n$/,/;
379 Storable - persistency for perl data structures
384 store \%table, 'file';
385 $hashref = retrieve('file');
387 use Storable qw(nstore store_fd nstore_fd freeze thaw dclone);
390 nstore \%table, 'file';
391 $hashref = retrieve('file'); # There is NO nretrieve()
393 # Storing to and retrieving from an already opened file
394 store_fd \@array, \*STDOUT;
395 nstore_fd \%table, \*STDOUT;
396 $aryref = fd_retrieve(\*SOCKET);
397 $hashref = fd_retrieve(\*SOCKET);
399 # Serializing to memory
400 $serialized = freeze \%table;
401 %table_clone = %{ thaw($serialized) };
403 # Deep (recursive) cloning
404 $cloneref = dclone($ref);
407 use Storable qw(lock_store lock_nstore lock_retrieve)
408 lock_store \%table, 'file';
409 lock_nstore \%table, 'file';
410 $hashref = lock_retrieve('file');
414 The Storable package brings persistency to your perl data structures
415 containing SCALAR, ARRAY, HASH or REF objects, i.e. anything that can be
416 convenientely stored to disk and retrieved at a later time.
418 It can be used in the regular procedural way by calling C<store> with
419 a reference to the object to be stored, along with the file name where
420 the image should be written.
421 The routine returns C<undef> for I/O problems or other internal error,
422 a true value otherwise. Serious errors are propagated as a C<die> exception.
424 To retrieve data stored to disk, use C<retrieve> with a file name,
425 and the objects stored into that file are recreated into memory for you,
426 a I<reference> to the root object being returned. In case an I/O error
427 occurs while reading, C<undef> is returned instead. Other serious
428 errors are propagated via C<die>.
430 Since storage is performed recursively, you might want to stuff references
431 to objects that share a lot of common data into a single array or hash
432 table, and then store that object. That way, when you retrieve back the
433 whole thing, the objects will continue to share what they originally shared.
435 At the cost of a slight header overhead, you may store to an already
436 opened file descriptor using the C<store_fd> routine, and retrieve
437 from a file via C<fd_retrieve>. Those names aren't imported by default,
438 so you will have to do that explicitely if you need those routines.
439 The file descriptor you supply must be already opened, for read
440 if you're going to retrieve and for write if you wish to store.
442 store_fd(\%table, *STDOUT) || die "can't store to stdout\n";
443 $hashref = fd_retrieve(*STDIN);
445 You can also store data in network order to allow easy sharing across
446 multiple platforms, or when storing on a socket known to be remotely
447 connected. The routines to call have an initial C<n> prefix for I<network>,
448 as in C<nstore> and C<nstore_fd>. At retrieval time, your data will be
449 correctly restored so you don't have to know whether you're restoring
450 from native or network ordered data. Double values are stored stringified
451 to ensure portability as well, at the slight risk of loosing some precision
452 in the last decimals.
454 When using C<fd_retrieve>, objects are retrieved in sequence, one
455 object (i.e. one recursive tree) per associated C<store_fd>.
457 If you're more from the object-oriented camp, you can inherit from
458 Storable and directly store your objects by invoking C<store> as
459 a method. The fact that the root of the to-be-stored tree is a
460 blessed reference (i.e. an object) is special-cased so that the
461 retrieve does not provide a reference to that object but rather the
462 blessed object reference itself. (Otherwise, you'd get a reference
463 to that blessed object).
467 The Storable engine can also store data into a Perl scalar instead, to
468 later retrieve them. This is mainly used to freeze a complex structure in
469 some safe compact memory place (where it can possibly be sent to another
470 process via some IPC, since freezing the structure also serializes it in
471 effect). Later on, and maybe somewhere else, you can thaw the Perl scalar
472 out and recreate the original complex structure in memory.
474 Surprisingly, the routines to be called are named C<freeze> and C<thaw>.
475 If you wish to send out the frozen scalar to another machine, use
476 C<nfreeze> instead to get a portable image.
478 Note that freezing an object structure and immediately thawing it
479 actually achieves a deep cloning of that structure:
481 dclone(.) = thaw(freeze(.))
483 Storable provides you with a C<dclone> interface which does not create
484 that intermediary scalar but instead freezes the structure in some
485 internal memory space and then immediatly thaws it out.
487 =head1 ADVISORY LOCKING
489 The C<lock_store> and C<lock_nstore> routine are equivalent to C<store>
490 and C<nstore>, only they get an exclusive lock on the file before
491 writing. Likewise, C<lock_retrieve> performs as C<retrieve>, but also
492 gets a shared lock on the file before reading.
494 Like with any advisory locking scheme, the protection only works if
495 you systematically use C<lock_store> and C<lock_retrieve>. If one
496 side of your application uses C<store> whilst the other uses C<lock_retrieve>,
497 you will get no protection at all.
499 The internal advisory locking is implemented using Perl's flock() routine.
500 If your system does not support any form of flock(), or if you share
501 your files across NFS, you might wish to use other forms of locking by
502 using modules like LockFile::Simple which lock a file using a filesystem
503 entry, instead of locking the file descriptor.
507 The heart of Storable is written in C for decent speed. Extra low-level
508 optimization have been made when manipulating perl internals, to
509 sacrifice encapsulation for the benefit of a greater speed.
511 =head1 CANONICAL REPRESENTATION
513 Normally Storable stores elements of hashes in the order they are
514 stored internally by Perl, i.e. pseudo-randomly. If you set
515 C<$Storable::canonical> to some C<TRUE> value, Storable will store
516 hashes with the elements sorted by their key. This allows you to
517 compare data structures by comparing their frozen representations (or
518 even the compressed frozen representations), which can be useful for
519 creating lookup tables for complicated queries.
521 Canonical order does not imply network order, those are two orthogonal
524 =head1 ERROR REPORTING
526 Storable uses the "exception" paradigm, in that it does not try to workaround
527 failures: if something bad happens, an exception is generated from the
528 caller's perspective (see L<Carp> and C<croak()>). Use eval {} to trap
531 When Storable croaks, it tries to report the error via the C<logcroak()>
532 routine from the C<Log::Agent> package, if it is available.
534 Normal errors are reported by having store() or retrieve() return C<undef>.
535 Such errors are usually I/O errors (or truncated stream errors at retrieval).
541 Any class may define hooks that will be called during the serialization
542 and deserialization process on objects that are instances of that class.
543 Those hooks can redefine the way serialization is performed (and therefore,
544 how the symetrical deserialization should be conducted).
546 Since we said earlier:
548 dclone(.) = thaw(freeze(.))
550 everything we say about hooks should also hold for deep cloning. However,
551 hooks get to know whether the operation is a mere serialization, or a cloning.
553 Therefore, when serializing hooks are involved,
555 dclone(.) <> thaw(freeze(.))
557 Well, you could keep them in sync, but there's no guarantee it will always
558 hold on classes somebody else wrote. Besides, there is little to gain in
559 doing so: a serializing hook could only keep one attribute of an object,
560 which is probably not what should happen during a deep cloning of that
563 Here is the hooking interface:
567 =item C<STORABLE_freeze> I<obj>, I<cloning>
569 The serializing hook, called on the object during serialization. It can be
570 inherited, or defined in the class itself, like any other method.
572 Arguments: I<obj> is the object to serialize, I<cloning> is a flag indicating
573 whether we're in a dclone() or a regular serialization via store() or freeze().
575 Returned value: A LIST C<($serialized, $ref1, $ref2, ...)> where $serialized
576 is the serialized form to be used, and the optional $ref1, $ref2, etc... are
577 extra references that you wish to let the Storable engine serialize.
579 At deserialization time, you will be given back the same LIST, but all the
580 extra references will be pointing into the deserialized structure.
582 The B<first time> the hook is hit in a serialization flow, you may have it
583 return an empty list. That will signal the Storable engine to further
584 discard that hook for this class and to therefore revert to the default
585 serialization of the underlying Perl data. The hook will again be normally
586 processed in the next serialization.
588 Unless you know better, serializing hook should always say:
590 sub STORABLE_freeze {
591 my ($self, $cloning) = @_;
592 return if $cloning; # Regular default serialization
596 in order to keep reasonable dclone() semantics.
598 =item C<STORABLE_thaw> I<obj>, I<cloning>, I<serialized>, ...
600 The deserializing hook called on the object during deserialization.
601 But wait. If we're deserializing, there's no object yet... right?
603 Wrong: the Storable engine creates an empty one for you. If you know Eiffel,
604 you can view C<STORABLE_thaw> as an alternate creation routine.
606 This means the hook can be inherited like any other method, and that
607 I<obj> is your blessed reference for this particular instance.
609 The other arguments should look familiar if you know C<STORABLE_freeze>:
610 I<cloning> is true when we're part of a deep clone operation, I<serialized>
611 is the serialized string you returned to the engine in C<STORABLE_freeze>,
612 and there may be an optional list of references, in the same order you gave
613 them at serialization time, pointing to the deserialized objects (which
614 have been processed courtesy of the Storable engine).
616 When the Storable engine does not find any C<STORABLE_thaw> hook routine,
617 it tries to load the class by requiring the package dynamically (using
618 the blessed package name), and then re-attempts the lookup. If at that
619 time the hook cannot be located, the engine croaks. Note that this mechanism
620 will fail if you define several classes in the same file, but perlmod(1)
623 It is up to you to use these information to populate I<obj> the way you want.
625 Returned value: none.
631 Predicates are not exportable. They must be called by explicitely prefixing
632 them with the Storable package name.
636 =item C<Storable::last_op_in_netorder>
638 The C<Storable::last_op_in_netorder()> predicate will tell you whether
639 network order was used in the last store or retrieve operation. If you
640 don't know how to use this, just forget about it.
642 =item C<Storable::is_storing>
644 Returns true if within a store operation (via STORABLE_freeze hook).
646 =item C<Storable::is_retrieving>
648 Returns true if within a retrieve operation, (via STORABLE_thaw hook).
654 With hooks comes the ability to recurse back to the Storable engine. Indeed,
655 hooks are regular Perl code, and Storable is convenient when it comes to
656 serialize and deserialize things, so why not use it to handle the
657 serialization string?
659 There are a few things you need to know however:
665 You can create endless loops if the things you serialize via freeze()
666 (for instance) point back to the object we're trying to serialize in the hook.
670 Shared references among objects will not stay shared: if we're serializing
671 the list of object [A, C] where both object A and C refer to the SAME object
672 B, and if there is a serializing hook in A that says freeze(B), then when
673 deserializing, we'll get [A', C'] where A' refers to B', but C' refers to D,
674 a deep clone of B'. The topology was not preserved.
678 That's why C<STORABLE_freeze> lets you provide a list of references
679 to serialize. The engine guarantees that those will be serialized in the
680 same context as the other objects, and therefore that shared objects will
683 In the above [A, C] example, the C<STORABLE_freeze> hook could return:
685 ("something", $self->{B})
687 and the B part would be serialized by the engine. In C<STORABLE_thaw>, you
688 would get back the reference to the B' object, deserialized for you.
690 Therefore, recursion should normally be avoided, but is nonetheless supported.
694 There is a new Clone module available on CPAN which implements deep cloning
695 natively, i.e. without freezing to memory and thawing the result. It is
696 aimed to replace Storable's dclone() some day. However, it does not currently
697 support Storable hooks to redefine the way deep cloning is performed.
699 =head1 Storable magic
701 Yes, there's a lot of that :-) But more precisely, in UNIX systems
702 there's a utility called C<file>, which recognizes data files based on
703 their contents (usually their first few bytes). For this to work,
704 a certain file called F<magic> needs to taught about the I<signature>
705 of the data. Where that configuration file lives depends on the UNIX
706 flavour, often it's something like F</usr/share/misc/magic> or
707 F</etc/magic>. Your system administrator needs to do the updating of
708 the F<magic> file. The necessary signature information is output to
709 stdout by invoking Storable::show_file_magic(). Note that the open
710 source implementation of the C<file> utility 3.38 (or later)
711 is expected to contain the support for recognising Storable files,
712 in addition to other kinds of Perl files.
716 Here are some code samples showing a possible usage of Storable:
718 use Storable qw(store retrieve freeze thaw dclone);
720 %color = ('Blue' => 0.1, 'Red' => 0.8, 'Black' => 0, 'White' => 1);
722 store(\%color, '/tmp/colors') or die "Can't store %a in /tmp/colors!\n";
724 $colref = retrieve('/tmp/colors');
725 die "Unable to retrieve from /tmp/colors!\n" unless defined $colref;
726 printf "Blue is still %lf\n", $colref->{'Blue'};
728 $colref2 = dclone(\%color);
730 $str = freeze(\%color);
731 printf "Serialization of %%color is %d bytes long.\n", length($str);
732 $colref3 = thaw($str);
734 which prints (on my machine):
736 Blue is still 0.100000
737 Serialization of %color is 102 bytes long.
741 If you're using references as keys within your hash tables, you're bound
742 to disapointment when retrieving your data. Indeed, Perl stringifies
743 references used as hash table keys. If you later wish to access the
744 items via another reference stringification (i.e. using the same
745 reference that was used for the key originally to record the value into
746 the hash table), it will work because both references stringify to the
749 It won't work across a C<store> and C<retrieve> operations however, because
750 the addresses in the retrieved objects, which are part of the stringified
751 references, will probably differ from the original addresses. The
752 topology of your structure is preserved, but not hidden semantics
755 On platforms where it matters, be sure to call C<binmode()> on the
756 descriptors that you pass to Storable functions.
758 Storing data canonically that contains large hashes can be
759 significantly slower than storing the same data normally, as
760 temprorary arrays to hold the keys for each hash have to be allocated,
761 populated, sorted and freed. Some tests have shown a halving of the
762 speed of storing -- the exact penalty will depend on the complexity of
763 your data. There is no slowdown on retrieval.
767 You can't store GLOB, CODE, FORMLINE, etc... If you can define
768 semantics for those operations, feel free to enhance Storable so that
769 it can deal with them.
771 The store functions will C<croak> if they run into such references
772 unless you set C<$Storable::forgive_me> to some C<TRUE> value. In that
773 case, the fatal message is turned in a warning and some
774 meaningless string is stored instead.
776 Setting C<$Storable::canonical> may not yield frozen strings that
777 compare equal due to possible stringification of numbers. When the
778 string version of a scalar exists, it is the form stored, therefore
779 if you happen to use your numbers as strings between two freezing
780 operations on the same data structures, you will get different
783 When storing doubles in network order, their value is stored as text.
784 However, you should also not expect non-numeric floating-point values
785 such as infinity and "not a number" to pass successfully through a
786 nstore()/retrieve() pair.
788 As Storable neither knows nor cares about character sets (although it
789 does know that characters may be more than eight bits wide), any difference
790 in the interpretation of character codes between a host and a target
791 system is your problem. In particular, if host and target use different
792 code points to represent the characters used in the text representation
793 of floating-point numbers, you will not be able be able to exchange
794 floating-point data, even with nstore().
798 Thank you to (in chronological order):
800 Jarkko Hietaniemi <jhi@iki.fi>
801 Ulrich Pfeifer <pfeifer@charly.informatik.uni-dortmund.de>
802 Benjamin A. Holzman <bah@ecnvantage.com>
803 Andrew Ford <A.Ford@ford-mason.co.uk>
804 Gisle Aas <gisle@aas.no>
805 Jeff Gresham <gresham_jeffrey@jpmorgan.com>
806 Murray Nesbitt <murray@activestate.com>
807 Marc Lehmann <pcg@opengroup.org>
808 Justin Banks <justinb@wamnet.com>
809 Jarkko Hietaniemi <jhi@iki.fi> (AGAIN, as perl 5.7.0 Pumpkin!)
810 Salvador Ortiz Garcia <sog@msg.com.mx>
811 Dominic Dunlop <domo@computer.org>
812 Erik Haugan <erik@solbors.no>
814 for their bug reports, suggestions and contributions.
816 Benjamin Holzman contributed the tied variable support, Andrew Ford
817 contributed the canonical order for hashes, and Gisle Aas fixed
818 a few misunderstandings of mine regarding the Perl internals,
819 and optimized the emission of "tags" in the output streams by
820 simply counting the objects instead of tagging them (leading to
821 a binary incompatibility for the Storable image starting at version
822 0.6--older images are of course still properly understood).
823 Murray Nesbitt made Storable thread-safe. Marc Lehmann added overloading
824 and reference to tied items support.
828 There is a Japanese translation of this man page available at
829 http://member.nifty.ne.jp/hippo2000/perltips/storable.htm ,
830 courtesy of Kawai, Takanori <kawai@nippon-rad.co.jp>.
834 Raphael Manfredi F<E<lt>Raphael_Manfredi@pobox.comE<gt>>