Profile of Variable/Magic.pm

Filename	/usr/local/lib/perl/5.18.2/Variable/Magic.pm
Statements	Executed 30 statements in 1.44ms

Subroutines
Calls	P	F	Exclusive Time	Inclusive Time	Subroutine
1	1	1	1.15ms	1.31ms	Variable::Magic::::BEGIN@688Variable::Magic::BEGIN@688
1	1	1	35µs	47µs	Variable::Magic::::wizardVariable::Magic::wizard
2	1	1	21µs	26µs	Variable::Magic::::castVariable::Magic::cast (xsub)
1	1	1	19µs	19µs	Variable::Magic::::BEGIN@3Variable::Magic::BEGIN@3
1	1	1	13µs	226µs	Variable::Magic::::BEGIN@213Variable::Magic::BEGIN@213
1	1	1	12µs	12µs	Variable::Magic::::_wizardVariable::Magic::_wizard (xsub)
1	1	1	9µs	26µs	Variable::Magic::::BEGIN@5Variable::Magic::BEGIN@5
1	1	1	9µs	14µs	Variable::Magic::::BEGIN@6Variable::Magic::BEGIN@6
2	1	1	6µs	6µs	Variable::Magic::::getdataVariable::Magic::getdata (xsub)
1	1	1	4µs	4µs	Variable::Magic::::BEGIN@19Variable::Magic::BEGIN@19

Call graph for these subroutines as a Graphviz dot language file.

Line	State ments	Time on line	Calls	Time in subs	Code
1					package Variable::Magic;
2
3	2	59µs	1	19µs	# spent 19µs within Variable::Magic::BEGIN@3 which was called: # once (19µs+0s) by B::Hooks::EndOfScope::XS::BEGIN@9 at line 3 use 5.008; # spent 19µs making 1 call to Variable::Magic::BEGIN@3
4
5	2	28µs	2	43µs	# spent 26µs (9+17) within Variable::Magic::BEGIN@5 which was called: # once (9µs+17µs) by B::Hooks::EndOfScope::XS::BEGIN@9 at line 5 use strict; # spent 26µs making 1 call to Variable::Magic::BEGIN@5 # spent 17µs making 1 call to strict::import
6	2	56µs	2	20µs	# spent 14µs (9+6) within Variable::Magic::BEGIN@6 which was called: # once (9µs+6µs) by B::Hooks::EndOfScope::XS::BEGIN@9 at line 6 use warnings; # spent 14µs making 1 call to Variable::Magic::BEGIN@6 # spent 6µs making 1 call to warnings::import
7
8					=head1 NAME
9
10					Variable::Magic - Associate user-defined magic to variables from Perl.
11
12					=head1 VERSION
13
14					Version 0.59
15
16					=cut
17
18	1	200ns			our $VERSION;
19					# spent 4µs within Variable::Magic::BEGIN@19 which was called: # once (4µs+0s) by B::Hooks::EndOfScope::XS::BEGIN@9 at line 21 BEGIN {
20	1	10µs			$VERSION = '0.59';
21	1	208µs	1	4µs	} # spent 4µs making 1 call to Variable::Magic::BEGIN@19
22
23					=head1 SYNOPSIS
24
25					use Variable::Magic qw<wizard cast VMG_OP_INFO_NAME>;
26
27					{ # A variable tracer
28					my $wiz = wizard(
29					set => sub { print "now set to ${$_[0]}!\n" },
30					free => sub { print "destroyed!\n" },
31					);
32
33					my $a = 1;
34					cast $a, $wiz;
35					$a = 2; # "now set to 2!"
36					} # "destroyed!"
37
38					{ # A hash with a default value
39					my $wiz = wizard(
40					data => sub { $_[1] },
41					fetch => sub { $_[2] = $_[1] unless exists $_[0]->{$_[2]}; () },
42					store => sub { print "key $_[2] stored in $_[-1]\n" },
43					copy_key => 1,
44					op_info => VMG_OP_INFO_NAME,
45					);
46
47					my %h = (_default => 0, apple => 2);
48					cast %h, $wiz, '_default';
49					print $h{banana}, "\n"; # "0" (there is no 'banana' key in %h)
50					$h{pear} = 1; # "key pear stored in helem"
51					}
52
53					=head1 DESCRIPTION
54
55					Magic is Perl's way of enhancing variables.
56					This mechanism lets the user add extra data to any variable and hook syntactical operations (such as access, assignment or destruction) that can be applied to it.
57					With this module, you can add your own magic to any variable without having to write a single line of XS.
58
59					You'll realize that these magic variables look a lot like tied variables.
60					It is not surprising, as tied variables are implemented as a special kind of magic, just like any 'irregular' Perl variable : scalars like C<$!>, C<$(> or C<$^W>, the C<%ENV> and C<%SIG> hashes, the C<@ISA> array, C<vec()> and C<substr()> lvalues, L<threads::shared> variables...
61					They all share the same underlying C API, and this module gives you direct access to it.
62
63					Still, the magic made available by this module differs from tieing and overloading in several ways :
64
65					=over 4
66
67					=item *
68
69					Magic is not copied on assignment.
70
71					You attach it to variables, not values (as for blessed references).
72
73					=item *
74
75					Magic does not replace the original semantics.
76
77					Magic callbacks usually get triggered before the original action takes place, and cannot prevent it from happening.
78					This also makes catching individual events easier than with C<tie>, where you have to provide fallbacks methods for all actions by usually inheriting from the correct C<Tie::Std*> class and overriding individual methods in your own class.
79
80					=item *
81
82					Magic is multivalued.
83
84					You can safely apply different kinds of magics to the same variable, and each of them will be invoked successively.
85
86					=item *
87
88					Magic is type-agnostic.
89
90					The same magic can be applied on scalars, arrays, hashes, subs or globs.
91					But the same hook (see below for a list) may trigger differently depending on the type of the variable.
92
93					=item *
94
95					Magic is invisible at Perl level.
96
97					Magical and non-magical variables cannot be distinguished with C<ref>, C<tied> or another trick.
98
99					=item *
100
101					Magic is notably faster.
102
103					Mainly because perl's way of handling magic is lighter by nature, and because there is no need for any method resolution.
104					Also, since you don't have to reimplement all the variable semantics, you only pay for what you actually use.
105
106					=back
107
108					The operations that can be overloaded are :
109
110					=over 4
111
112					=item *
113
114					I<get>
115
116					This magic is invoked when the variable is evaluated.
117					It is never called for arrays and hashes.
118
119					=item *
120
121					I<set>
122
123					This magic is called each time the value of the variable changes.
124					It is called for array subscripts and slices, but never for hashes.
125
126					=item *
127
128					I<len>
129
130					This magic only applies to arrays (though it used to also apply to scalars), and is triggered when the 'size' or the 'length' of the variable has to be known by Perl.
131					This is typically the magic involved when an array is evaluated in scalar context, but also on array assignment and loops (C<for>, C<map> or C<grep>).
132					The length is returned from the callback as an integer.
133
134					Starting from perl 5.12, this magic is no longer called by the C<length> keyword, and starting from perl 5.17.4 it is also no longer called for scalars in any situation, making this magic only meaningful on arrays.
135					You can use the constants L</VMG_COMPAT_SCALAR_LENGTH_NOLEN> and L</VMG_COMPAT_SCALAR_NOLEN> to see if this magic is available for scalars or not.
136
137					=item *
138
139					I<clear>
140
141					This magic is invoked when the variable is reset, such as when an array is emptied.
142					Please note that this is different from undefining the variable, even though the magic is called when the clearing is a result of the undefine (e.g. for an array, but actually a bug prevent it to work before perl 5.9.5 - see the L<history\|/PERL MAGIC HISTORY>).
143
144					=item *
145
146					I<free>
147
148					This magic is called when a variable is destroyed as the result of going out of scope (but not when it is undefined).
149					It behaves roughly like Perl object destructors (i.e. C<DESTROY> methods), except that exceptions thrown from inside a I<free> callback will always be propagated to the surrounding code.
150
151					=item *
152
153					I<copy>
154
155					When applied to tied arrays and hashes, this magic fires when you try to access or change their elements.
156
157					Starting from perl 5.17.0, it can also be applied to closure prototypes, in which case the magic will be called when the prototype is cloned.
158					The L</VMG_COMPAT_CODE_COPY_CLONE> constant is true when your perl support this feature.
159
160					=item *
161
162					I<dup>
163
164					This magic is invoked when the variable is cloned across threads.
165					It is currently not available.
166
167					=item *
168
169					I<local>
170
171					When this magic is set on a variable, all subsequent localizations of the variable will trigger the callback.
172					It is available on your perl if and only if C<MGf_LOCAL> is true.
173
174					=back
175
176					The following actions only apply to hashes and are available if and only if L</VMG_UVAR> is true.
177					They are referred to as I<uvar> magics.
178
179					=over 4
180
181					=item *
182
183					I<fetch>
184
185					This magic is invoked each time an element is fetched from the hash.
186
187					=item *
188
189					I<store>
190
191					This one is called when an element is stored into the hash.
192
193					=item *
194
195					I<exists>
196
197					This magic fires when a key is tested for existence in the hash.
198
199					=item *
200
201					I<delete>
202
203					This magic is triggered when a key is deleted in the hash, regardless of whether the key actually exists in it.
204
205					=back
206
207					You can refer to the tests to have more insight of where the different magics are invoked.
208
209					=head1 FUNCTIONS
210
211					=cut
212
213					# spent 226µs (13+213) within Variable::Magic::BEGIN@213 which was called: # once (13µs+213µs) by B::Hooks::EndOfScope::XS::BEGIN@9 at line 216 BEGIN {
214	1	500ns			require XSLoader;
215	1	224µs	1	213µs	XSLoader::load(__PACKAGE__, $VERSION); # spent 213µs making 1 call to XSLoader::load
216	1	516µs	1	226µs	} # spent 226µs making 1 call to Variable::Magic::BEGIN@213
217
218					=head2 C<wizard>
219
220					wizard(
221					data => sub { ... },
222					get => sub { my ($ref, $data [, $op]) = @_; ... },
223					set => sub { my ($ref, $data [, $op]) = @_; ... },
224					len => sub {
225					my ($ref, $data, $len [, $op]) = @_; ... ; return $newlen
226					},
227					clear => sub { my ($ref, $data [, $op]) = @_; ... },
228					free => sub { my ($ref, $data [, $op]) = @_, ... },
229					copy => sub { my ($ref, $data, $key, $elt [, $op]) = @_; ... },
230					local => sub { my ($ref, $data [, $op]) = @_; ... },
231					fetch => sub { my ($ref, $data, $key [, $op]) = @_; ... },
232					store => sub { my ($ref, $data, $key [, $op]) = @_; ... },
233					exists => sub { my ($ref, $data, $key [, $op]) = @_; ... },
234					delete => sub { my ($ref, $data, $key [, $op]) = @_; ... },
235					copy_key => $bool,
236					op_info => [ 0 \| VMG_OP_INFO_NAME \| VMG_OP_INFO_OBJECT ],
237					)
238
239					This function creates a 'wizard', an opaque object that holds the magic information.
240					It takes a list of keys / values as argument, whose keys can be :
241
242					=over 4
243
244					=item *
245
246					C<data>
247
248					A code (or string) reference to a private data constructor.
249					It is called in scalar context each time the magic is cast onto a variable, with C<$_[0]> being a reference to this variable and C<@_[1 .. @_-1]> being all extra arguments that were passed to L</cast>.
250					The scalar returned from this call is then attached to the variable and can be retrieved later with L</getdata>.
251
252					=item *
253
254					C<get>, C<set>, C<len>, C<clear>, C<free>, C<copy>, C<local>, C<fetch>, C<store>, C<exists> and C<delete>
255
256					Code (or string) references to the respective magic callbacks.
257					You don't have to specify all of them : the magic corresponding to undefined entries will simply not be hooked.
258
259					When those callbacks are executed, C<$_[0]> is a reference to the magic variable and C<$_[1]> is the associated private data (or C<undef> when no private data constructor is supplied with the wizard).
260					Other arguments depend on which kind of magic is involved :
261
262					=over 8
263
264					=item *
265
266					I<len>
267
268					C<$_[2]> contains the natural, non-magical length of the variable (which can only be a scalar or an array as I<len> magic is only relevant for these types).
269					The callback is expected to return the new scalar or array length to use, or C<undef> to default to the normal length.
270
271					=item *
272
273					I<copy>
274
275					When the variable for which the magic is invoked is an array or an hash, C<$_[2]> is a either an alias or a copy of the current key, and C<$_[3]> is an alias to the current element (i.e. the value).
276					Since C<$_[2]> might be a copy, it is useless to try to change it or cast magic on it.
277
278					Starting from perl 5.17.0, this magic can also be called for code references.
279					In this case, C<$_[2]> is always C<undef> and C<$_[3]> is a reference to the cloned anonymous subroutine.
280
281					=item *
282
283					I<fetch>, I<store>, I<exists> and I<delete>
284
285					C<$_[2]> is an alias to the current key.
286					Note that C<$_[2]> may rightfully be readonly if the key comes from a bareword, and as such it is unsafe to assign to it.
287					You can ask for a copy instead by passing C<< copy_key => 1 >> to L</wizard> which, at the price of a small performance hit, allows you to safely assign to C<$_[2]> in order to e.g. redirect the action to another key.
288
289					=back
290
291					Finally, if C<< op_info => $num >> is also passed to C<wizard>, then one extra element is appended to C<@_>.
292					Its nature depends on the value of C<$num> :
293
294					=over 8
295
296					=item *
297
298					C<VMG_OP_INFO_NAME>
299
300					C<$_[-1]> is the current op name.
301
302					=item *
303
304					C<VMG_OP_INFO_OBJECT>
305
306					C<$_[-1]> is the C<B::OP> object for the current op.
307
308					=back
309
310					Both result in a small performance hit, but just getting the name is lighter than getting the op object.
311
312					These callbacks are always executed in scalar context.
313					The returned value is coerced into a signed integer, which is then passed straight to the perl magic API.
314					However, note that perl currently only cares about the return value of the I<len> magic callback and ignores all the others.
315					Starting with Variable::Magic 0.58, a reference returned from a non-I<len> magic callback will not be destroyed immediately but will be allowed to survive until the end of the statement that triggered the magic.
316					This lets you use this return value as a token for triggering a destructor after the original magic action takes place.
317					You can see an example of this technique in the L<cookbook\|/COOKBOOK>.
318
319					=back
320
321					Each callback can be specified as :
322
323					=over 4
324
325					=item *
326
327					a code reference, which will be called as a subroutine.
328
329					=item *
330
331					a string reference, where the string denotes which subroutine is to be called when magic is triggered.
332					If the subroutine name is not fully qualified, then the current package at the time the magic is invoked will be used instead.
333
334					=item *
335
336					a reference to C<undef>, in which case a no-op magic callback is installed instead of the default one.
337					This may especially be helpful for I<local> magic, where an empty callback prevents magic from being copied during localization.
338
339					=back
340
341					Note that I<free> magic is never called during global destruction, as there is no way to ensure that the wizard object and the callback were not destroyed before the variable.
342
343					Here is a simple usage example :
344
345					# A simple scalar tracer
346					my $wiz = wizard(
347					get => sub { print STDERR "got ${$_[0]}\n" },
348					set => sub { print STDERR "set to ${$_[0]}\n" },
349					free => sub { print STDERR "${$_[0]} was deleted\n" },
350					);
351
352					=cut
353
354					# spent 47µs (35+12) within Variable::Magic::wizard which was called: # once (35µs+12µs) by Module::Runtime::require_module at line 24 of B/Hooks/EndOfScope/XS.pm sub wizard {
355	1	5µs			if (@_ % 2) {
356					require Carp;
357					Carp::croak('Wrong number of arguments for wizard()');
358					}
359
360	1	3µs			my %opts = @_;
361
362	1	2µs			my @keys = qw<op_info data get set len clear free copy dup>;
363	1	900ns			push @keys, 'local' if MGf_LOCAL;
364	1	2µs			push @keys, qw<fetch store exists delete copy_key> if VMG_UVAR;
365
366	1	200ns			my ($wiz, $err);
367					{
368	2	900ns			local $@;
369	2	27µs	1	12µs	$wiz = eval { _wizard(map $opts{$_}, @keys) }; # spent 12µs making 1 call to Variable::Magic::_wizard
370	1	900ns			$err = $@;
371					}
372	1	300ns			if ($err) {
373					$err =~ s/\sat\s+.*?\n//;
374					require Carp;
375					Carp::croak($err);
376					}
377
378	1	6µs			return $wiz;
379					}
380
381					=head2 C<cast>
382
383					cast [$@%&*]var, $wiz, @args
384
385					This function associates C<$wiz> magic to the supplied variable, without overwriting any other kind of magic.
386					It returns true on success or when C<$wiz> magic is already attached, and croaks on error.
387					When C<$wiz> provides a data constructor, it is called just before magic is cast onto the variable, and it receives a reference to the target variable in C<$_[0]> and the content of C<@args> in C<@_[1 .. @args]>.
388					Otherwise, C<@args> is ignored.
389
390					# Casts $wiz onto $x, passing (\$x, '1') to the data constructor.
391					my $x;
392					cast $x, $wiz, 1;
393
394					The C<var> argument can be an array or hash value.
395					Magic for these scalars behaves like for any other, except that it is dispelled when the entry is deleted from the container.
396					For example, if you want to call C<POSIX::tzset> each time the C<'TZ'> environment variable is changed in C<%ENV>, you can use :
397
398					use POSIX;
399					cast $ENV{TZ}, wizard set => sub { POSIX::tzset(); () };
400
401					If you want to handle the possible deletion of the C<'TZ'> entry, you must also specify I<store> magic.
402
403					=head2 C<getdata>
404
405					getdata [$@%&*]var, $wiz
406
407					This accessor fetches the private data associated with the magic C<$wiz> in the variable.
408					It croaks when C<$wiz> does not represent a valid magic object, and returns an empty list if no such magic is attached to the variable or when the wizard has no data constructor.
409
410					# Get the data attached to $wiz in $x, or undef if $wiz
411					# did not attach any.
412					my $data = getdata $x, $wiz;
413
414					=head2 C<dispell>
415
416					dispell [$@%&*]variable, $wiz
417
418					The exact opposite of L</cast> : it dissociates C<$wiz> magic from the variable.
419					This function returns true on success, C<0> when no magic represented by C<$wiz> could be found in the variable, and croaks if the supplied wizard is invalid.
420
421					# Dispell now.
422					die 'no such magic in $x' unless dispell $x, $wiz;
423
424					=head1 CONSTANTS
425
426					=head2 C<MGf_COPY>
427
428					Evaluates to true if and only if the I<copy> magic is available.
429					This is the case for perl 5.7.3 and greater, which is ensured by the requirements of this module.
430
431					=head2 C<MGf_DUP>
432
433					Evaluates to true if and only if the I<dup> magic is available.
434					This is the case for perl 5.7.3 and greater, which is ensured by the requirements of this module.
435
436					=head2 C<MGf_LOCAL>
437
438					Evaluates to true if and only if the I<local> magic is available.
439					This is the case for perl 5.9.3 and greater.
440
441					=head2 C<VMG_UVAR>
442
443					When this constant is true, you can use the I<fetch>, I<store>, I<exists> and I<delete> magics on hashes.
444					Initial L</VMG_UVAR> capability was introduced in perl 5.9.5, with a fully functional implementation shipped with perl 5.10.0.
445
446					=head2 C<VMG_COMPAT_SCALAR_LENGTH_NOLEN>
447
448					True for perls that don't call I<len> magic when taking the C<length> of a magical scalar.
449
450					=head2 C<VMG_COMPAT_SCALAR_NOLEN>
451
452					True for perls that don't call I<len> magic on scalars.
453					Implies L</VMG_COMPAT_SCALAR_LENGTH_NOLEN>.
454
455					=head2 C<VMG_COMPAT_ARRAY_PUSH_NOLEN>
456
457					True for perls that don't call I<len> magic when you push an element in a magical array.
458					Starting from perl 5.11.0, this only refers to pushes in non-void context and hence is false.
459
460					=head2 C<VMG_COMPAT_ARRAY_PUSH_NOLEN_VOID>
461
462					True for perls that don't call I<len> magic when you push in void context an element in a magical array.
463
464					=head2 C<VMG_COMPAT_ARRAY_UNSHIFT_NOLEN_VOID>
465
466					True for perls that don't call I<len> magic when you unshift in void context an element in a magical array.
467
468					=head2 C<VMG_COMPAT_ARRAY_UNDEF_CLEAR>
469
470					True for perls that call I<clear> magic when undefining magical arrays.
471
472					=head2 C<VMG_COMPAT_HASH_DELETE_NOUVAR_VOID>
473
474					True for perls that don't call I<delete> magic when you delete an element from a hash in void context.
475
476					=head2 C<VMG_COMPAT_CODE_COPY_CLONE>
477
478					True for perls that call I<copy> magic when a magical closure prototype is cloned.
479
480					=head2 C<VMG_COMPAT_GLOB_GET>
481
482					True for perls that call I<get> magic for operations on globs.
483
484					=head2 C<VMG_PERL_PATCHLEVEL>
485
486					The perl patchlevel this module was built with, or C<0> for non-debugging perls.
487
488					=head2 C<VMG_THREADSAFE>
489
490					True if and only if this module could have been built with thread-safety features enabled.
491
492					=head2 C<VMG_FORKSAFE>
493
494					True if and only if this module could have been built with fork-safety features enabled.
495					This is always true except on Windows where it is false for perl 5.10.0 and below.
496
497					=head2 C<VMG_OP_INFO_NAME>
498
499					Value to pass with C<op_info> to get the current op name in the magic callbacks.
500
501					=head2 C<VMG_OP_INFO_OBJECT>
502
503					Value to pass with C<op_info> to get a C<B::OP> object representing the current op in the magic callbacks.
504
505					=head1 COOKBOOK
506
507					=head2 Associate an object to any perl variable
508
509					This technique can be useful for passing user data through limited APIs.
510					It is similar to using inside-out objects, but without the drawback of having to implement a complex destructor.
511
512					{
513					package Magical::UserData;
514
515					use Variable::Magic qw<wizard cast getdata>;
516
517					my $wiz = wizard data => sub { \$_[1] };
518
519					sub ud (\[$@%*&]) : lvalue {
520					my ($var) = @_;
521					my $data = &getdata($var, $wiz);
522					unless (defined $data) {
523					$data = \(my $slot);
524					&cast($var, $wiz, $slot)
525					or die "Couldn't cast UserData magic onto the variable";
526					}
527					$$data;
528					}
529					}
530
531					{
532					BEGIN { *ud = \&Magical::UserData::ud }
533
534					my $cb;
535					$cb = sub { print 'Hello, ', ud(&$cb), "!\n" };
536
537					ud(&$cb) = 'world';
538					$cb->(); # Hello, world!
539					}
540
541					=head2 Recursively cast magic on datastructures
542
543					C<cast> can be called from any magical callback, and in particular from C<data>.
544					This allows you to recursively cast magic on datastructures :
545
546					my $wiz;
547					$wiz = wizard data => sub {
548					my ($var, $depth) = @_;
549					$depth \|\|= 0;
550					my $r = ref $var;
551					if ($r eq 'ARRAY') {
552					&cast((ref() ? $_ : \$_), $wiz, $depth + 1) for @$var;
553					} elsif ($r eq 'HASH') {
554					&cast((ref() ? $_ : \$_), $wiz, $depth + 1) for values %$var;
555					}
556					return $depth;
557					},
558					free => sub {
559					my ($var, $depth) = @_;
560					my $r = ref $var;
561					print "free $r at depth $depth\n";
562					();
563					};
564
565					{
566					my %h = (
567					a => [ 1, 2 ],
568					b => { c => 3 }
569					);
570					cast %h, $wiz;
571					}
572
573					When C<%h> goes out of scope, this prints something among the lines of :
574
575					free HASH at depth 0
576					free HASH at depth 1
577					free SCALAR at depth 2
578					free ARRAY at depth 1
579					free SCALAR at depth 3
580					free SCALAR at depth 3
581
582					Of course, this example does nothing with the values that are added after the C<cast>.
583
584					=head2 Delayed magic actions
585
586					Starting with Variable::Magic 0.58, the return value of the magic callbacks can be used to delay the action until after the original action takes place :
587
588					my $delayed;
589					my $delayed_aux = wizard(
590					data => sub { $_[1] },
591					free => sub {
592					my ($target) = $_[1];
593					my $target_data = &getdata($target, $delayed);
594					local $target_data->{guard} = 1;
595					if (ref $target eq 'SCALAR') {
596					my $orig = $$target;
597					$$target = $target_data->{mangler}->($orig);
598					}
599					return;
600					},
601					);
602					$delayed = wizard(
603					data => sub {
604					return +{ guard => 0, mangler => $_[1] };
605					},
606					set => sub {
607					return if $_[1]->{guard};
608					my $token;
609					cast $token, $delayed_aux, $_[0];
610					return \$token;
611					},
612					);
613					my $x = 1;
614					cast $x, $delayed => sub { $_[0] * 2 };
615					$x = 2;
616					# $x is now 4
617					# But note that the delayed action only takes place at the end of the
618					# current statement :
619					my @y = ($x = 5, $x);
620					# $x is now 10, but @y is (5, 5)
621
622					=head1 PERL MAGIC HISTORY
623
624					The places where magic is invoked have changed a bit through perl history.
625					Here is a little list of the most recent ones.
626
627					=over 4
628
629					=item *
630
631					B<5.6.x>
632
633					I<p14416> : I<copy> and I<dup> magic.
634
635					=item *
636
637					B<5.8.9>
638
639					I<p28160> : Integration of I<p25854> (see below).
640
641					I<p32542> : Integration of I<p31473> (see below).
642
643					=item *
644
645					B<5.9.3>
646
647					I<p25854> : I<len> magic is no longer called when pushing an element into a magic array.
648
649					I<p26569> : I<local> magic.
650
651					=item *
652
653					B<5.9.5>
654
655					I<p31064> : Meaningful I<uvar> magic.
656
657					I<p31473> : I<clear> magic was not invoked when undefining an array.
658					The bug is fixed as of this version.
659
660					=item *
661
662					B<5.10.0>
663
664					Since C<PERL_MAGIC_uvar> is uppercased, C<hv_magic_check()> triggers I<copy> magic on hash stores for (non-tied) hashes that also have I<uvar> magic.
665
666					=item *
667
668					B<5.11.x>
669
670					I<p32969> : I<len> magic is no longer invoked when calling C<length> with a magical scalar.
671
672					I<p34908> : I<len> magic is no longer called when pushing / unshifting an element into a magical array in void context.
673					The C<push> part was already covered by I<p25854>.
674
675					I<g9cdcb38b> : I<len> magic is called again when pushing into a magical array in non-void context.
676
677					=back
678
679					=head1 EXPORT
680
681					The functions L</wizard>, L</cast>, L</getdata> and L</dispell> are only exported on request.
682					All of them are exported by the tags C<':funcs'> and C<':all'>.
683
684					All the constants are also only exported on request, either individually or by the tags C<':consts'> and C<':all'>.
685
686					=cut
687
688	2	263µs	2	1.40ms	# spent 1.31ms (1.15+158µs) within Variable::Magic::BEGIN@688 which was called: # once (1.15ms+158µs) by B::Hooks::EndOfScope::XS::BEGIN@9 at line 688 use base qw<Exporter>; # spent 1.31ms making 1 call to Variable::Magic::BEGIN@688 # spent 87µs making 1 call to base::import
689
690	1	900ns			our @EXPORT = ();
691	1	7µs			our %EXPORT_TAGS = (
692					'funcs' => [ qw<wizard cast getdata dispell> ],
693					'consts' => [ qw<
694					MGf_COPY MGf_DUP MGf_LOCAL VMG_UVAR
695					VMG_COMPAT_SCALAR_LENGTH_NOLEN
696					VMG_COMPAT_SCALAR_NOLEN
697					VMG_COMPAT_ARRAY_PUSH_NOLEN VMG_COMPAT_ARRAY_PUSH_NOLEN_VOID
698					VMG_COMPAT_ARRAY_UNSHIFT_NOLEN_VOID
699					VMG_COMPAT_ARRAY_UNDEF_CLEAR
700					VMG_COMPAT_HASH_DELETE_NOUVAR_VOID
701					VMG_COMPAT_CODE_COPY_CLONE
702					VMG_COMPAT_GLOB_GET
703					VMG_PERL_PATCHLEVEL
704					VMG_THREADSAFE VMG_FORKSAFE
705					VMG_OP_INFO_NAME VMG_OP_INFO_OBJECT
706					> ],
707					);
708	1	8µs			our @EXPORT_OK = map { @$_ } values %EXPORT_TAGS;
709	1	4µs			$EXPORT_TAGS{'all'} = [ @EXPORT_OK ];
710
711					=head1 CAVEATS
712
713					In order to hook hash operations with magic, you need at least perl 5.10.0 (see L</VMG_UVAR>).
714
715					If you want to store a magic object in the private data slot, you will not be able to recover the magic with L</getdata>, since magic is not copied by assignment.
716					You can work around this gotcha by storing a reference to the magic object instead.
717
718					If you define a wizard with I<free> magic and cast it on itself, it results in a memory cycle, so this destructor will not be called when the wizard is freed.
719
720					=head1 DEPENDENCIES
721
722					L<perl> 5.8.
723
724					A C compiler.
725					This module may happen to build with a C++ compiler as well, but don't rely on it, as no guarantee is made in this regard.
726
727					L<Carp> (core since perl 5), L<XSLoader> (since 5.6.0).
728
729					=head1 SEE ALSO
730
731					L<perlguts> and L<perlapi> for internal information about magic.
732
733					L<perltie> and L<overload> for other ways of enhancing objects.
734
735					=head1 AUTHOR
736
737					Vincent Pit, C<< <perl at profvince.com> >>, L<http://www.profvince.com>.
738
739					You can contact me by mail or on C<irc.perl.org> (vincent).
740
741					=head1 BUGS
742
743					Please report any bugs or feature requests to C<bug-variable-magic at rt.cpan.org>, or through the web interface at L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Variable-Magic>.
744					I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
745
746					=head1 SUPPORT
747
748					You can find documentation for this module with the perldoc command.
749
750					perldoc Variable::Magic
751
752					=head1 COPYRIGHT & LICENSE
753
754					Copyright 2007,2008,2009,2010,2011,2012,2013,2014,2015 Vincent Pit, all rights reserved.
755
756					This program is free software; you can redistribute it and/or modify it
757					under the same terms as Perl itself.
758
759					=cut
760
761	1	8µs			1; # End of Variable::Magic

					# spent 12µs within Variable::Magic::_wizard which was called: # once (12µs+0s) by Variable::Magic::wizard at line 369 sub Variable::Magic::_wizard; # xsub
					# spent 26µs (21+4) within Variable::Magic::cast which was called 2 times, avg 13µs/call: # 2 times (21µs+4µs) by B::Hooks::EndOfScope::XS::on_scope_end at line 36 of B/Hooks/EndOfScope/XS.pm, avg 13µs/call sub Variable::Magic::cast; # xsub
					# spent 6µs within Variable::Magic::getdata which was called 2 times, avg 3µs/call: # 2 times (6µs+0s) by B::Hooks::EndOfScope::XS::on_scope_end at line 32 of B/Hooks/EndOfScope/XS.pm, avg 3µs/call sub Variable::Magic::getdata; # xsub