1 package Attribute::Handlers;
10 my ($pkg, $ref, $type) = @_;
11 return $symcache{$pkg,$ref} if $symcache{$pkg,$ref};
14 foreach my $sym ( values %{$pkg."::"} ) {
15 return $symcache{$pkg,$ref} = \$sym
16 if *{$sym}{$type} && *{$sym}{$type} == $ref;
21 VAR => [qw[SCALAR ARRAY HASH]],
22 ANY => [qw[SCALAR ARRAY HASH CODE]],
23 "" => [qw[SCALAR ARRAY HASH CODE]],
24 SCALAR => [qw[SCALAR]],
33 my %sigil = (SCALAR=>'$', ARRAY=>'@', HASH=>'%');
41 my @global_phases = qw(BEGIN CHECK INIT END);
44 croak "Usage: use $_[0] autotie => {AttrName => TieClassName,...}";
47 my $qual_id = qr/^[_a-z]\w*(::[_a-z]\w*)*$/i;
51 return unless $class eq "Attribute::Handlers";
54 if ($cmd =~ /^autotie((?:ref)?)$/) {
55 my $tiedata = ($1 ? '$ref, ' : '') . '@$data';
57 _usage_AH_ $class unless ref($mapping) eq 'HASH';
58 while (my($attr, $tieclass) = each %$mapping) {
59 $tieclass =~ s/^([_a-z]\w*(::[_a-z]\w*)*)(.*)/$1/is;
61 _usage_AH_ $class unless $attr =~ $qual_id
62 && $tieclass =~ $qual_id
63 && eval "use base $tieclass; 1";
64 if ($tieclass->isa('Exporter')) {
65 local $Exporter::ExportLevel = 2;
66 $tieclass->import(eval $args);
68 $attr =~ s/__CALLER__/caller(1)/e;
69 $attr = caller()."::".$attr unless $attr =~ /::/;
71 sub $attr : ATTR(VAR) {
72 my (\$ref, \$data) = \@_[2,4];
73 my \$was_arrayref = ref \$data eq 'ARRAY';
74 \$data = [ \$data ] unless \$was_arrayref;
75 my \$type = ref(\$ref)||"value (".(\$ref||"<undef>").")";
76 (\$type eq 'SCALAR')? tie \$\$ref,'$tieclass',$tiedata
77 :(\$type eq 'ARRAY') ? tie \@\$ref,'$tieclass',$tiedata
78 :(\$type eq 'HASH') ? tie \%\$ref,'$tieclass',$tiedata
79 : die "Can't autotie a \$type\n"
81 } or die "Internal error: $@";
85 croak "Can't understand $_";
89 sub _resolve_lastattr {
90 return unless $lastattr{ref};
91 my $sym = findsym @lastattr{'pkg','ref'}
92 or die "Internal error: $lastattr{pkg} symbol went missing";
93 my $name = *{$sym}{NAME};
94 warn "Declaration of $name attribute in package $lastattr{pkg} may clash with future reserved word\n"
95 if $^W and $name !~ /[A-Z]/;
96 foreach ( @{$validtype{$lastattr{type}}} ) {
97 *{"$lastattr{pkg}::_ATTR_${_}_${name}"} = $lastattr{ref};
103 return if $AUTOLOAD =~ /::DESTROY$/;
104 my ($class) = $AUTOLOAD =~ m/(.*)::/g;
105 $AUTOLOAD =~ m/_ATTR_(.*?)_(.*)/ or
106 croak "Can't locate class method '$AUTOLOAD' via package '$class'";
107 croak "Attribute handler '$2' doesn't handle $1 attributes";
110 my $builtin = qr/lvalue|method|locked|unique|shared/;
112 sub _gen_handler_AH_() {
115 my ($pkg, $ref, @attrs) = @_;
116 my (undef, $filename, $linenum) = caller 2;
118 my ($attr, $data) = /^([a-z_]\w*)(?:[(](.*)[)])?$/is or next;
119 if ($attr eq 'ATTR') {
121 $raw{$ref} = $data =~ s/\s*,?\s*RAWDATA\s*,?\s*//;
122 $phase{$ref}{BEGIN} = 1
123 if $data =~ s/\s*,?\s*(BEGIN)\s*,?\s*//;
124 $phase{$ref}{INIT} = 1
125 if $data =~ s/\s*,?\s*(INIT)\s*,?\s*//;
126 $phase{$ref}{END} = 1
127 if $data =~ s/\s*,?\s*(END)\s*,?\s*//;
128 $phase{$ref}{CHECK} = 1
129 if $data =~ s/\s*,?\s*(CHECK)\s*,?\s*//
130 || ! keys %{$phase{$ref}};
131 # Added for cleanup to not pollute next call.
133 croak "Can't have two ATTR specifiers on one subroutine"
135 croak "Bad attribute type: ATTR($data)"
136 unless $validtype{$data};
137 %lastattr=(pkg=>$pkg,ref=>$ref,type=>$data);
141 my $handler = $pkg->can("_ATTR_${type}_${attr}");
142 next unless $handler;
143 my $decl = [$pkg, $ref, $attr, $data,
144 $raw{$handler}, $phase{$handler}, $filename, $linenum];
145 foreach my $gphase (@global_phases) {
146 _apply_handler_AH_($decl,$gphase)
147 if $global_phases{$gphase} <= $global_phase;
149 if ($global_phase != 0) {
150 # if _gen_handler_AH_ is being called after
151 # CHECK it's for a lexical, so make sure
152 # it didn't want to run anything later
154 local $Carp::CarpLevel = 2;
155 carp "Won't be able to apply END handler"
156 if $phase{$handler}{END};
159 push @declarations, $decl
164 return grep {defined && !/$builtin/} @attrs;
168 *{"Attribute::Handlers::UNIVERSAL::MODIFY_${_}_ATTRIBUTES"} =
169 _gen_handler_AH_ foreach @{$validtype{ANY}};
170 push @UNIVERSAL::ISA, 'Attribute::Handlers::UNIVERSAL'
171 unless grep /^Attribute::Handlers::UNIVERSAL$/, @UNIVERSAL::ISA;
173 sub _apply_handler_AH_ {
174 my ($declaration, $phase) = @_;
175 my ($pkg, $ref, $attr, $data, $raw, $handlerphase, $filename, $linenum) = @$declaration;
176 return unless $handlerphase->{$phase};
177 # print STDERR "Handling $attr on $ref in $phase with [$data]\n";
179 my $handler = "_ATTR_${type}_${attr}";
180 my $sym = findsym($pkg, $ref);
181 $sym ||= $type eq 'CODE' ? 'ANON' : 'LEXICAL';
183 my $evaled = !$raw && eval("package $pkg; no warnings;
184 local \$SIG{__WARN__}=sub{die}; [$data]");
185 $data = ($evaled && $data =~ /^\s*\[/) ? [$evaled]
186 : ($evaled) ? $evaled
189 (ref $sym eq 'GLOB' ? *{$sym}{ref $ref}||$ref : $ref),
191 (@$data>1? $data : $data->[0]),
204 _apply_handler_AH_($_,'CHECK') foreach @declarations;
209 _apply_handler_AH_($_,'INIT') foreach @declarations
213 END { $global_phase++; _apply_handler_AH_($_,'END') foreach @declarations }
220 Attribute::Handlers - Simpler definition of attribute handlers
224 This document describes version 0.78 of Attribute::Handlers,
225 released October 5, 2002.
231 use Attribute::Handlers;
232 no warnings 'redefine';
235 sub Good : ATTR(SCALAR) {
236 my ($package, $symbol, $referent, $attr, $data) = @_;
238 # Invoked for any scalar variable with a :Good attribute,
239 # provided the variable was declared in MyClass (or
240 # a derived class) or typed to MyClass.
242 # Do whatever to $referent here (executed in CHECK phase).
246 sub Bad : ATTR(SCALAR) {
247 # Invoked for any scalar variable with a :Bad attribute,
248 # provided the variable was declared in MyClass (or
249 # a derived class) or typed to MyClass.
253 sub Good : ATTR(ARRAY) {
254 # Invoked for any array variable with a :Good attribute,
255 # provided the variable was declared in MyClass (or
256 # a derived class) or typed to MyClass.
260 sub Good : ATTR(HASH) {
261 # Invoked for any hash variable with a :Good attribute,
262 # provided the variable was declared in MyClass (or
263 # a derived class) or typed to MyClass.
267 sub Ugly : ATTR(CODE) {
268 # Invoked for any subroutine declared in MyClass (or a
269 # derived class) with an :Ugly attribute.
274 # Invoked for any scalar, array, hash, or subroutine
275 # with an :Omni attribute, provided the variable or
276 # subroutine was declared in MyClass (or a derived class)
277 # or the variable was typed to MyClass.
278 # Use ref($_[2]) to determine what kind of referent it was.
283 use Attribute::Handlers autotie => { Cycle => Tie::Cycle };
285 my $next : Cycle(['A'..'Z']);
290 This module, when inherited by a package, allows that package's class to
291 define attribute handler subroutines for specific attributes. Variables
292 and subroutines subsequently defined in that package, or in packages
293 derived from that package may be given attributes with the same names as
294 the attribute handler subroutines, which will then be called in one of
295 the compilation phases (i.e. in a C<BEGIN>, C<CHECK>, C<INIT>, or C<END>
296 block). (C<UNITCHECK> blocks don't correspond to a global compilation
297 phase, so they can't be specified here.)
299 To create a handler, define it as a subroutine with the same name as
300 the desired attribute, and declare the subroutine itself with the
301 attribute C<:ATTR>. For example:
304 use Attribute::Handlers;
307 my ($package, $symbol, $referent, $attr, $data, $phase, $filename, $linenum) = @_;
310 *{$symbol}{NAME}, " ",
311 "($referent) ", "was just declared ",
312 "and ascribed the ${attr} attribute ",
313 "with data ($data)\n",
315 "in file $filename at line $linenum\n";
318 This creates a handler for the attribute C<:Loud> in the class LoudDecl.
319 Thereafter, any subroutine declared with a C<:Loud> attribute in the class
326 causes the above handler to be invoked, and passed:
332 the name of the package into which it was declared;
336 a reference to the symbol table entry (typeglob) containing the subroutine;
340 a reference to the subroutine;
344 the name of the attribute;
348 any data associated with that attribute;
352 the name of the phase in which the handler is being invoked;
356 the filename in which the handler is being invoked;
360 the line number in this file.
364 Likewise, declaring any variables with the C<:Loud> attribute within the
373 will cause the handler to be called with a similar argument list (except,
374 of course, that C<$_[2]> will be a reference to the variable).
376 The package name argument will typically be the name of the class into
377 which the subroutine was declared, but it may also be the name of a derived
378 class (since handlers are inherited).
380 If a lexical variable is given an attribute, there is no symbol table to
381 which it belongs, so the symbol table argument (C<$_[1]>) is set to the
382 string C<'LEXICAL'> in that case. Likewise, ascribing an attribute to
383 an anonymous subroutine results in a symbol table argument of C<'ANON'>.
385 The data argument passes in the value (if any) associated with the
386 attribute. For example, if C<&foo> had been declared:
388 sub foo :Loud("turn it up to 11, man!") {...}
390 then the string C<"turn it up to 11, man!"> would be passed as the
393 Attribute::Handlers makes strenuous efforts to convert
394 the data argument (C<$_[4]>) to a useable form before passing it to
395 the handler (but see L<"Non-interpretive attribute handlers">).
396 For example, all of these:
398 sub foo :Loud(till=>ears=>are=>bleeding) {...}
399 sub foo :Loud(['till','ears','are','bleeding']) {...}
400 sub foo :Loud(qw/till ears are bleeding/) {...}
401 sub foo :Loud(qw/my, ears, are, bleeding/) {...}
402 sub foo :Loud(till,ears,are,bleeding) {...}
404 causes it to pass C<['till','ears','are','bleeding']> as the handler's
405 data argument. However, if the data can't be parsed as valid Perl, then
406 it is passed as an uninterpreted string. For example:
408 sub foo :Loud(my,ears,are,bleeding) {...}
409 sub foo :Loud(qw/my ears are bleeding) {...}
411 cause the strings C<'my,ears,are,bleeding'> and C<'qw/my ears are bleeding'>
412 respectively to be passed as the data argument.
414 If the attribute has only a single associated scalar data value, that value is
415 passed as a scalar. If multiple values are associated, they are passed as an
416 array reference. If no value is associated with the attribute, C<undef> is
420 =head2 Typed lexicals
422 Regardless of the package in which it is declared, if a lexical variable is
423 ascribed an attribute, the handler that is invoked is the one belonging to
424 the package to which it is typed. For example, the following declarations:
428 my LoudDecl $loudobj : Loud;
429 my LoudDecl @loudobjs : Loud;
430 my LoudDecl %loudobjex : Loud;
432 causes the LoudDecl::Loud handler to be invoked (even if OtherClass also
433 defines a handler for C<:Loud> attributes).
436 =head2 Type-specific attribute handlers
438 If an attribute handler is declared and the C<:ATTR> specifier is
439 given the name of a built-in type (C<SCALAR>, C<ARRAY>, C<HASH>, or C<CODE>),
440 the handler is only applied to declarations of that type. For example,
441 the following definition:
445 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
447 creates an attribute handler that applies only to scalars:
453 my $metal : RealLoud; # invokes &LoudDecl::RealLoud
454 my @metal : RealLoud; # error: unknown attribute
455 my %metal : RealLoud; # error: unknown attribute
456 sub metal : RealLoud {...} # error: unknown attribute
458 You can, of course, declare separate handlers for these types as well
459 (but you'll need to specify C<no warnings 'redefine'> to do it quietly):
462 use Attribute::Handlers;
463 no warnings 'redefine';
465 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
466 sub RealLoud :ATTR(ARRAY) { print "Urrrrrrrrrr!" }
467 sub RealLoud :ATTR(HASH) { print "Arrrrrgggghhhhhh!" }
468 sub RealLoud :ATTR(CODE) { croak "Real loud sub torpedoed" }
470 You can also explicitly indicate that a single handler is meant to be
471 used for all types of referents like so:
474 use Attribute::Handlers;
476 sub SeriousLoud :ATTR(ANY) { warn "Hearing loss imminent" }
478 (I.e. C<ATTR(ANY)> is a synonym for C<:ATTR>).
481 =head2 Non-interpretive attribute handlers
483 Occasionally the strenuous efforts Attribute::Handlers makes to convert
484 the data argument (C<$_[4]>) to a useable form before passing it to
485 the handler get in the way.
487 You can turn off that eagerness-to-help by declaring
488 an attribute handler with the keyword C<RAWDATA>. For example:
490 sub Raw : ATTR(RAWDATA) {...}
491 sub Nekkid : ATTR(SCALAR,RAWDATA) {...}
492 sub Au::Naturale : ATTR(RAWDATA,ANY) {...}
494 Then the handler makes absolutely no attempt to interpret the data it
495 receives and simply passes it as a string:
497 my $power : Raw(1..100); # handlers receives "1..100"
499 =head2 Phase-specific attribute handlers
501 By default, attribute handlers are called at the end of the compilation
502 phase (in a C<CHECK> block). This seems to be optimal in most cases because
503 most things that can be defined are defined by that point but nothing has
506 However, it is possible to set up attribute handlers that are called at
507 other points in the program's compilation or execution, by explicitly
508 stating the phase (or phases) in which you wish the attribute handler to
509 be called. For example:
511 sub Early :ATTR(SCALAR,BEGIN) {...}
512 sub Normal :ATTR(SCALAR,CHECK) {...}
513 sub Late :ATTR(SCALAR,INIT) {...}
514 sub Final :ATTR(SCALAR,END) {...}
515 sub Bookends :ATTR(SCALAR,BEGIN,END) {...}
517 As the last example indicates, a handler may be set up to be (re)called in
518 two or more phases. The phase name is passed as the handler's final argument.
520 Note that attribute handlers that are scheduled for the C<BEGIN> phase
521 are handled as soon as the attribute is detected (i.e. before any
522 subsequently defined C<BEGIN> blocks are executed).
525 =head2 Attributes as C<tie> interfaces
527 Attributes make an excellent and intuitive interface through which to tie
528 variables. For example:
530 use Attribute::Handlers;
533 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
534 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
535 $data = [ $data ] unless ref $data eq 'ARRAY';
536 tie $$referent, 'Tie::Cycle', $data;
543 my $next : Cycle('A'..'Z'); # $next is now a tied variable
549 Note that, because the C<Cycle> attribute receives its arguments in the
550 C<$data> variable, if the attribute is given a list of arguments, C<$data>
551 will consist of a single array reference; otherwise, it will consist of the
552 single argument directly. Since Tie::Cycle requires its cycling values to
553 be passed as an array reference, this means that we need to wrap
554 non-array-reference arguments in an array constructor:
556 $data = [ $data ] unless ref $data eq 'ARRAY';
558 Typically, however, things are the other way around: the tieable class expects
559 its arguments as a flattened list, so the attribute looks like:
561 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
562 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
563 my @data = ref $data eq 'ARRAY' ? @$data : $data;
564 tie $$referent, 'Tie::Whatever', @data;
568 This software pattern is so widely applicable that Attribute::Handlers
569 provides a way to automate it: specifying C<'autotie'> in the
570 C<use Attribute::Handlers> statement. So, the cycling example,
571 could also be written:
573 use Attribute::Handlers autotie => { Cycle => 'Tie::Cycle' };
579 my $next : Cycle(['A'..'Z']); # $next is now a tied variable
584 Note that we now have to pass the cycling values as an array reference,
585 since the C<autotie> mechanism passes C<tie> a list of arguments as a list
586 (as in the Tie::Whatever example), I<not> as an array reference (as in
587 the original Tie::Cycle example at the start of this section).
589 The argument after C<'autotie'> is a reference to a hash in which each key is
590 the name of an attribute to be created, and each value is the class to which
591 variables ascribed that attribute should be tied.
593 Note that there is no longer any need to import the Tie::Cycle module --
594 Attribute::Handlers takes care of that automagically. You can even pass
595 arguments to the module's C<import> subroutine, by appending them to the
596 class name. For example:
598 use Attribute::Handlers
599 autotie => { Dir => 'Tie::Dir qw(DIR_UNLINK)' };
601 If the attribute name is unqualified, the attribute is installed in the
602 current package. Otherwise it is installed in the qualifier's package:
606 use Attribute::Handlers autotie => {
607 Other::Good => Tie::SecureHash, # tie attr installed in Other::
608 Bad => Tie::Taxes, # tie attr installed in Here::
609 UNIVERSAL::Ugly => Software::Patent # tie attr installed everywhere
612 Autoties are most commonly used in the module to which they actually tie,
613 and need to export their attributes to any module that calls them. To
614 facilitate this, Attribute::Handlers recognizes a special "pseudo-class" --
615 C<__CALLER__>, which may be specified as the qualifier of an attribute:
617 package Tie::Me::Kangaroo:Down::Sport;
619 use Attribute::Handlers autotie => { '__CALLER__::Roo' => __PACKAGE__ };
621 This causes Attribute::Handlers to define the C<Roo> attribute in the package
622 that imports the Tie::Me::Kangaroo:Down::Sport module.
624 Note that it is important to quote the __CALLER__::Roo identifier because
625 a bug in perl 5.8 will refuse to parse it and cause an unknown error.
627 =head3 Passing the tied object to C<tie>
629 Occasionally it is important to pass a reference to the object being tied
630 to the TIESCALAR, TIEHASH, etc. that ties it.
632 The C<autotie> mechanism supports this too. The following code:
634 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
635 my $var : Selfish(@args);
637 has the same effect as:
639 tie my $var, 'Tie::Selfish', @args;
641 But when C<"autotieref"> is used instead of C<"autotie">:
643 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
644 my $var : Selfish(@args);
646 the effect is to pass the C<tie> call an extra reference to the variable
649 tie my $var, 'Tie::Selfish', \$var, @args;
655 If the class shown in L<SYNOPSIS> were placed in the MyClass.pm
656 module, then the following code:
661 my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
663 package SomeOtherClass;
668 sub fn :Ugly(sister) :Omni('po',tent()) {...}
669 my @arr :Good :Omni(s/cie/nt/);
670 my %hsh :Good(q/bye) :Omni(q/bus/);
673 would cause the following handlers to be invoked:
675 # my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
677 MyClass::Good:ATTR(SCALAR)( 'MyClass', # class
678 'LEXICAL', # no typeglob
682 'CHECK', # compiler phase
685 MyClass::Bad:ATTR(SCALAR)( 'MyClass', # class
686 'LEXICAL', # no typeglob
690 'CHECK', # compiler phase
693 MyClass::Omni:ATTR(SCALAR)( 'MyClass', # class
694 'LEXICAL', # no typeglob
697 '-vorous' # eval'd attr data
698 'CHECK', # compiler phase
702 # sub fn :Ugly(sister) :Omni('po',tent()) {...}
704 MyClass::UGLY:ATTR(CODE)( 'SomeOtherClass', # class
705 \*SomeOtherClass::fn, # typeglob
706 \&SomeOtherClass::fn, # referent
708 'sister' # eval'd attr data
709 'CHECK', # compiler phase
712 MyClass::Omni:ATTR(CODE)( 'SomeOtherClass', # class
713 \*SomeOtherClass::fn, # typeglob
714 \&SomeOtherClass::fn, # referent
716 ['po','acle'] # eval'd attr data
717 'CHECK', # compiler phase
721 # my @arr :Good :Omni(s/cie/nt/);
723 MyClass::Good:ATTR(ARRAY)( 'SomeOtherClass', # class
724 'LEXICAL', # no typeglob
728 'CHECK', # compiler phase
731 MyClass::Omni:ATTR(ARRAY)( 'SomeOtherClass', # class
732 'LEXICAL', # no typeglob
735 "" # eval'd attr data
736 'CHECK', # compiler phase
740 # my %hsh :Good(q/bye) :Omni(q/bus/);
742 MyClass::Good:ATTR(HASH)( 'SomeOtherClass', # class
743 'LEXICAL', # no typeglob
746 'q/bye' # raw attr data
747 'CHECK', # compiler phase
750 MyClass::Omni:ATTR(HASH)( 'SomeOtherClass', # class
751 'LEXICAL', # no typeglob
754 'bus' # eval'd attr data
755 'CHECK', # compiler phase
759 Installing handlers into UNIVERSAL, makes them...err..universal.
762 package Descriptions;
763 use Attribute::Handlers;
766 sub name { return $name{$_[2]}||*{$_[1]}{NAME} }
768 sub UNIVERSAL::Name :ATTR {
769 $name{$_[2]} = $_[4];
772 sub UNIVERSAL::Purpose :ATTR {
773 print STDERR "Purpose of ", &name, " is $_[4]\n";
776 sub UNIVERSAL::Unit :ATTR {
777 print STDERR &name, " measured in $_[4]\n";
784 my $capacity : Name(capacity)
785 : Purpose(to store max storage capacity for files)
791 sub foo : Purpose(to foo all data before barring it) { }
800 =item C<Bad attribute type: ATTR(%s)>
802 An attribute handler was specified with an C<:ATTR(I<ref_type>)>, but the
803 type of referent it was defined to handle wasn't one of the five permitted:
804 C<SCALAR>, C<ARRAY>, C<HASH>, C<CODE>, or C<ANY>.
806 =item C<Attribute handler %s doesn't handle %s attributes>
808 A handler for attributes of the specified name I<was> defined, but not
809 for the specified type of declaration. Typically encountered whe trying
810 to apply a C<VAR> attribute handler to a subroutine, or a C<SCALAR>
811 attribute handler to some other type of variable.
813 =item C<Declaration of %s attribute in package %s may clash with future reserved word>
815 A handler for an attributes with an all-lowercase name was declared. An
816 attribute with an all-lowercase name might have a meaning to Perl
817 itself some day, even though most don't yet. Use a mixed-case attribute
820 =item C<Can't have two ATTR specifiers on one subroutine>
822 You just can't, okay?
823 Instead, put all the specifications together with commas between them
824 in a single C<ATTR(I<specification>)>.
826 =item C<Can't autotie a %s>
828 You can only declare autoties for types C<"SCALAR">, C<"ARRAY">, and
829 C<"HASH">. They're the only things (apart from typeglobs -- which are
830 not declarable) that Perl can tie.
832 =item C<Internal error: %s symbol went missing>
834 Something is rotten in the state of the program. An attributed
835 subroutine ceased to exist between the point it was declared and the point
836 at which its attribute handler(s) would have been called.
838 =item C<Won't be able to apply END handler>
840 You have defined an END handler for an attribute that is being applied
841 to a lexical variable. Since the variable may not be available during END
848 Damian Conway (damian@conway.org)
852 There are undoubtedly serious bugs lurking somewhere in code this funky :-)
853 Bug reports and other feedback are most welcome.
857 Copyright (c) 2001, Damian Conway. All Rights Reserved.
858 This module is free software. It may be used, redistributed
859 and/or modified under the same terms as Perl itself.