1 package Attribute::Handlers;
6 use vars qw($VERSION $AUTOLOAD);
12 my ($pkg, $ref, $type) = @_;
13 return $symcache{$pkg,$ref} if $symcache{$pkg,$ref};
17 foreach my $sym ( values %{$pkg."::"} ) {
19 next unless ref ( \$sym ) eq 'GLOB';
20 return $symcache{$pkg,$ref} = \$sym
21 if *{$sym}{$type} && *{$sym}{$type} == $ref;
26 VAR => [qw[SCALAR ARRAY HASH]],
27 ANY => [qw[SCALAR ARRAY HASH CODE]],
28 "" => [qw[SCALAR ARRAY HASH CODE]],
29 SCALAR => [qw[SCALAR]],
38 my %sigil = (SCALAR=>'$', ARRAY=>'@', HASH=>'%');
46 my @global_phases = qw(BEGIN CHECK INIT END);
49 croak "Usage: use $_[0] autotie => {AttrName => TieClassName,...}";
52 my $qual_id = qr/^[_a-z]\w*(::[_a-z]\w*)*$/i;
56 return unless $class eq "Attribute::Handlers";
59 if ($cmd =~ /^autotie((?:ref)?)$/) {
60 my $tiedata = ($1 ? '$ref, ' : '') . '@$data';
62 _usage_AH_ $class unless ref($mapping) eq 'HASH';
63 while (my($attr, $tieclass) = each %$mapping) {
64 $tieclass =~ s/^([_a-z]\w*(::[_a-z]\w*)*)(.*)/$1/is;
66 _usage_AH_ $class unless $attr =~ $qual_id
67 && $tieclass =~ $qual_id
68 && eval "use base q\0$tieclass\0; 1";
69 if ($tieclass->isa('Exporter')) {
70 local $Exporter::ExportLevel = 2;
71 $tieclass->import(eval $args);
73 $attr =~ s/__CALLER__/caller(1)/e;
74 $attr = caller()."::".$attr unless $attr =~ /::/;
76 sub $attr : ATTR(VAR) {
77 my (\$ref, \$data) = \@_[2,4];
78 my \$was_arrayref = ref \$data eq 'ARRAY';
79 \$data = [ \$data ] unless \$was_arrayref;
80 my \$type = ref(\$ref)||"value (".(\$ref||"<undef>").")";
81 (\$type eq 'SCALAR')? tie \$\$ref,'$tieclass',$tiedata
82 :(\$type eq 'ARRAY') ? tie \@\$ref,'$tieclass',$tiedata
83 :(\$type eq 'HASH') ? tie \%\$ref,'$tieclass',$tiedata
84 : die "Can't autotie a \$type\n"
86 } or die "Internal error: $@";
90 croak "Can't understand $_";
94 sub _resolve_lastattr {
95 return unless $lastattr{ref};
96 my $sym = findsym @lastattr{'pkg','ref'}
97 or die "Internal error: $lastattr{pkg} symbol went missing";
98 my $name = *{$sym}{NAME};
99 warn "Declaration of $name attribute in package $lastattr{pkg} may clash with future reserved word\n"
100 if $^W and $name !~ /[A-Z]/;
101 foreach ( @{$validtype{$lastattr{type}}} ) {
103 *{"$lastattr{pkg}::_ATTR_${_}_${name}"} = $lastattr{ref};
109 return if $AUTOLOAD =~ /::DESTROY$/;
110 my ($class) = $AUTOLOAD =~ m/(.*)::/g;
111 $AUTOLOAD =~ m/_ATTR_(.*?)_(.*)/ or
112 croak "Can't locate class method '$AUTOLOAD' via package '$class'";
113 croak "Attribute handler '$2' doesn't handle $1 attributes";
116 my $builtin = qr/lvalue|method|locked|unique|shared/;
118 sub _gen_handler_AH_() {
121 my ($pkg, $ref, @attrs) = @_;
122 my (undef, $filename, $linenum) = caller 2;
124 my ($attr, $data) = /^([a-z_]\w*)(?:[(](.*)[)])?$/is or next;
125 if ($attr eq 'ATTR') {
128 $raw{$ref} = $data =~ s/\s*,?\s*RAWDATA\s*,?\s*//;
129 $phase{$ref}{BEGIN} = 1
130 if $data =~ s/\s*,?\s*(BEGIN)\s*,?\s*//;
131 $phase{$ref}{INIT} = 1
132 if $data =~ s/\s*,?\s*(INIT)\s*,?\s*//;
133 $phase{$ref}{END} = 1
134 if $data =~ s/\s*,?\s*(END)\s*,?\s*//;
135 $phase{$ref}{CHECK} = 1
136 if $data =~ s/\s*,?\s*(CHECK)\s*,?\s*//
137 || ! keys %{$phase{$ref}};
138 # Added for cleanup to not pollute next call.
140 croak "Can't have two ATTR specifiers on one subroutine"
142 croak "Bad attribute type: ATTR($data)"
143 unless $validtype{$data};
144 %lastattr=(pkg=>$pkg,ref=>$ref,type=>$data);
148 my $handler = $pkg->can("_ATTR_${type}_${attr}");
149 next unless $handler;
150 my $decl = [$pkg, $ref, $attr, $data,
151 $raw{$handler}, $phase{$handler}, $filename, $linenum];
152 foreach my $gphase (@global_phases) {
153 _apply_handler_AH_($decl,$gphase)
154 if $global_phases{$gphase} <= $global_phase;
156 if ($global_phase != 0) {
157 # if _gen_handler_AH_ is being called after
158 # CHECK it's for a lexical, so make sure
159 # it didn't want to run anything later
161 local $Carp::CarpLevel = 2;
162 carp "Won't be able to apply END handler"
163 if $phase{$handler}{END};
166 push @declarations, $decl
171 return grep {defined && !/$builtin/} @attrs;
177 *{"Attribute::Handlers::UNIVERSAL::MODIFY_${_}_ATTRIBUTES"} =
178 _gen_handler_AH_ foreach @{$validtype{ANY}};
180 push @UNIVERSAL::ISA, 'Attribute::Handlers::UNIVERSAL'
181 unless grep /^Attribute::Handlers::UNIVERSAL$/, @UNIVERSAL::ISA;
183 sub _apply_handler_AH_ {
184 my ($declaration, $phase) = @_;
185 my ($pkg, $ref, $attr, $data, $raw, $handlerphase, $filename, $linenum) = @$declaration;
186 return unless $handlerphase->{$phase};
187 # print STDERR "Handling $attr on $ref in $phase with [$data]\n";
189 my $handler = "_ATTR_${type}_${attr}";
190 my $sym = findsym($pkg, $ref);
191 $sym ||= $type eq 'CODE' ? 'ANON' : 'LEXICAL';
193 my $evaled = !$raw && eval("package $pkg; no warnings;
194 local \$SIG{__WARN__}=sub{die}; [$data]");
195 $data = ($evaled && $data =~ /^\s*\[/) ? [$evaled]
196 : ($evaled) ? $evaled
199 (ref $sym eq 'GLOB' ? *{$sym}{ref $ref}||$ref : $ref),
201 (@$data>1? $data : $data->[0]),
214 _apply_handler_AH_($_,'CHECK') foreach @declarations;
219 _apply_handler_AH_($_,'INIT') foreach @declarations
223 END { $global_phase++; _apply_handler_AH_($_,'END') foreach @declarations }
230 Attribute::Handlers - Simpler definition of attribute handlers
234 This document describes version 0.78 of Attribute::Handlers,
235 released October 5, 2002.
241 use Attribute::Handlers;
242 no warnings 'redefine';
245 sub Good : ATTR(SCALAR) {
246 my ($package, $symbol, $referent, $attr, $data) = @_;
248 # Invoked for any scalar variable with a :Good attribute,
249 # provided the variable was declared in MyClass (or
250 # a derived class) or typed to MyClass.
252 # Do whatever to $referent here (executed in CHECK phase).
256 sub Bad : ATTR(SCALAR) {
257 # Invoked for any scalar variable with a :Bad attribute,
258 # provided the variable was declared in MyClass (or
259 # a derived class) or typed to MyClass.
263 sub Good : ATTR(ARRAY) {
264 # Invoked for any array variable with a :Good attribute,
265 # provided the variable was declared in MyClass (or
266 # a derived class) or typed to MyClass.
270 sub Good : ATTR(HASH) {
271 # Invoked for any hash variable with a :Good attribute,
272 # provided the variable was declared in MyClass (or
273 # a derived class) or typed to MyClass.
277 sub Ugly : ATTR(CODE) {
278 # Invoked for any subroutine declared in MyClass (or a
279 # derived class) with an :Ugly attribute.
284 # Invoked for any scalar, array, hash, or subroutine
285 # with an :Omni attribute, provided the variable or
286 # subroutine was declared in MyClass (or a derived class)
287 # or the variable was typed to MyClass.
288 # Use ref($_[2]) to determine what kind of referent it was.
293 use Attribute::Handlers autotie => { Cycle => Tie::Cycle };
295 my $next : Cycle(['A'..'Z']);
300 This module, when inherited by a package, allows that package's class to
301 define attribute handler subroutines for specific attributes. Variables
302 and subroutines subsequently defined in that package, or in packages
303 derived from that package may be given attributes with the same names as
304 the attribute handler subroutines, which will then be called in one of
305 the compilation phases (i.e. in a C<BEGIN>, C<CHECK>, C<INIT>, or C<END>
306 block). (C<UNITCHECK> blocks don't correspond to a global compilation
307 phase, so they can't be specified here.)
309 To create a handler, define it as a subroutine with the same name as
310 the desired attribute, and declare the subroutine itself with the
311 attribute C<:ATTR>. For example:
314 use Attribute::Handlers;
317 my ($package, $symbol, $referent, $attr, $data, $phase, $filename, $linenum) = @_;
320 *{$symbol}{NAME}, " ",
321 "($referent) ", "was just declared ",
322 "and ascribed the ${attr} attribute ",
323 "with data ($data)\n",
325 "in file $filename at line $linenum\n";
328 This creates a handler for the attribute C<:Loud> in the class LoudDecl.
329 Thereafter, any subroutine declared with a C<:Loud> attribute in the class
336 causes the above handler to be invoked, and passed:
342 the name of the package into which it was declared;
346 a reference to the symbol table entry (typeglob) containing the subroutine;
350 a reference to the subroutine;
354 the name of the attribute;
358 any data associated with that attribute;
362 the name of the phase in which the handler is being invoked;
366 the filename in which the handler is being invoked;
370 the line number in this file.
374 Likewise, declaring any variables with the C<:Loud> attribute within the
383 will cause the handler to be called with a similar argument list (except,
384 of course, that C<$_[2]> will be a reference to the variable).
386 The package name argument will typically be the name of the class into
387 which the subroutine was declared, but it may also be the name of a derived
388 class (since handlers are inherited).
390 If a lexical variable is given an attribute, there is no symbol table to
391 which it belongs, so the symbol table argument (C<$_[1]>) is set to the
392 string C<'LEXICAL'> in that case. Likewise, ascribing an attribute to
393 an anonymous subroutine results in a symbol table argument of C<'ANON'>.
395 The data argument passes in the value (if any) associated with the
396 attribute. For example, if C<&foo> had been declared:
398 sub foo :Loud("turn it up to 11, man!") {...}
400 then the string C<"turn it up to 11, man!"> would be passed as the
403 Attribute::Handlers makes strenuous efforts to convert
404 the data argument (C<$_[4]>) to a useable form before passing it to
405 the handler (but see L<"Non-interpretive attribute handlers">).
406 For example, all of these:
408 sub foo :Loud(till=>ears=>are=>bleeding) {...}
409 sub foo :Loud(['till','ears','are','bleeding']) {...}
410 sub foo :Loud(qw/till ears are bleeding/) {...}
411 sub foo :Loud(qw/my, ears, are, bleeding/) {...}
412 sub foo :Loud(till,ears,are,bleeding) {...}
414 causes it to pass C<['till','ears','are','bleeding']> as the handler's
415 data argument. However, if the data can't be parsed as valid Perl, then
416 it is passed as an uninterpreted string. For example:
418 sub foo :Loud(my,ears,are,bleeding) {...}
419 sub foo :Loud(qw/my ears are bleeding) {...}
421 cause the strings C<'my,ears,are,bleeding'> and C<'qw/my ears are bleeding'>
422 respectively to be passed as the data argument.
424 If the attribute has only a single associated scalar data value, that value is
425 passed as a scalar. If multiple values are associated, they are passed as an
426 array reference. If no value is associated with the attribute, C<undef> is
430 =head2 Typed lexicals
432 Regardless of the package in which it is declared, if a lexical variable is
433 ascribed an attribute, the handler that is invoked is the one belonging to
434 the package to which it is typed. For example, the following declarations:
438 my LoudDecl $loudobj : Loud;
439 my LoudDecl @loudobjs : Loud;
440 my LoudDecl %loudobjex : Loud;
442 causes the LoudDecl::Loud handler to be invoked (even if OtherClass also
443 defines a handler for C<:Loud> attributes).
446 =head2 Type-specific attribute handlers
448 If an attribute handler is declared and the C<:ATTR> specifier is
449 given the name of a built-in type (C<SCALAR>, C<ARRAY>, C<HASH>, or C<CODE>),
450 the handler is only applied to declarations of that type. For example,
451 the following definition:
455 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
457 creates an attribute handler that applies only to scalars:
463 my $metal : RealLoud; # invokes &LoudDecl::RealLoud
464 my @metal : RealLoud; # error: unknown attribute
465 my %metal : RealLoud; # error: unknown attribute
466 sub metal : RealLoud {...} # error: unknown attribute
468 You can, of course, declare separate handlers for these types as well
469 (but you'll need to specify C<no warnings 'redefine'> to do it quietly):
472 use Attribute::Handlers;
473 no warnings 'redefine';
475 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
476 sub RealLoud :ATTR(ARRAY) { print "Urrrrrrrrrr!" }
477 sub RealLoud :ATTR(HASH) { print "Arrrrrgggghhhhhh!" }
478 sub RealLoud :ATTR(CODE) { croak "Real loud sub torpedoed" }
480 You can also explicitly indicate that a single handler is meant to be
481 used for all types of referents like so:
484 use Attribute::Handlers;
486 sub SeriousLoud :ATTR(ANY) { warn "Hearing loss imminent" }
488 (I.e. C<ATTR(ANY)> is a synonym for C<:ATTR>).
491 =head2 Non-interpretive attribute handlers
493 Occasionally the strenuous efforts Attribute::Handlers makes to convert
494 the data argument (C<$_[4]>) to a useable form before passing it to
495 the handler get in the way.
497 You can turn off that eagerness-to-help by declaring
498 an attribute handler with the keyword C<RAWDATA>. For example:
500 sub Raw : ATTR(RAWDATA) {...}
501 sub Nekkid : ATTR(SCALAR,RAWDATA) {...}
502 sub Au::Naturale : ATTR(RAWDATA,ANY) {...}
504 Then the handler makes absolutely no attempt to interpret the data it
505 receives and simply passes it as a string:
507 my $power : Raw(1..100); # handlers receives "1..100"
509 =head2 Phase-specific attribute handlers
511 By default, attribute handlers are called at the end of the compilation
512 phase (in a C<CHECK> block). This seems to be optimal in most cases because
513 most things that can be defined are defined by that point but nothing has
516 However, it is possible to set up attribute handlers that are called at
517 other points in the program's compilation or execution, by explicitly
518 stating the phase (or phases) in which you wish the attribute handler to
519 be called. For example:
521 sub Early :ATTR(SCALAR,BEGIN) {...}
522 sub Normal :ATTR(SCALAR,CHECK) {...}
523 sub Late :ATTR(SCALAR,INIT) {...}
524 sub Final :ATTR(SCALAR,END) {...}
525 sub Bookends :ATTR(SCALAR,BEGIN,END) {...}
527 As the last example indicates, a handler may be set up to be (re)called in
528 two or more phases. The phase name is passed as the handler's final argument.
530 Note that attribute handlers that are scheduled for the C<BEGIN> phase
531 are handled as soon as the attribute is detected (i.e. before any
532 subsequently defined C<BEGIN> blocks are executed).
535 =head2 Attributes as C<tie> interfaces
537 Attributes make an excellent and intuitive interface through which to tie
538 variables. For example:
540 use Attribute::Handlers;
543 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
544 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
545 $data = [ $data ] unless ref $data eq 'ARRAY';
546 tie $$referent, 'Tie::Cycle', $data;
553 my $next : Cycle('A'..'Z'); # $next is now a tied variable
559 Note that, because the C<Cycle> attribute receives its arguments in the
560 C<$data> variable, if the attribute is given a list of arguments, C<$data>
561 will consist of a single array reference; otherwise, it will consist of the
562 single argument directly. Since Tie::Cycle requires its cycling values to
563 be passed as an array reference, this means that we need to wrap
564 non-array-reference arguments in an array constructor:
566 $data = [ $data ] unless ref $data eq 'ARRAY';
568 Typically, however, things are the other way around: the tieable class expects
569 its arguments as a flattened list, so the attribute looks like:
571 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
572 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
573 my @data = ref $data eq 'ARRAY' ? @$data : $data;
574 tie $$referent, 'Tie::Whatever', @data;
578 This software pattern is so widely applicable that Attribute::Handlers
579 provides a way to automate it: specifying C<'autotie'> in the
580 C<use Attribute::Handlers> statement. So, the cycling example,
581 could also be written:
583 use Attribute::Handlers autotie => { Cycle => 'Tie::Cycle' };
589 my $next : Cycle(['A'..'Z']); # $next is now a tied variable
594 Note that we now have to pass the cycling values as an array reference,
595 since the C<autotie> mechanism passes C<tie> a list of arguments as a list
596 (as in the Tie::Whatever example), I<not> as an array reference (as in
597 the original Tie::Cycle example at the start of this section).
599 The argument after C<'autotie'> is a reference to a hash in which each key is
600 the name of an attribute to be created, and each value is the class to which
601 variables ascribed that attribute should be tied.
603 Note that there is no longer any need to import the Tie::Cycle module --
604 Attribute::Handlers takes care of that automagically. You can even pass
605 arguments to the module's C<import> subroutine, by appending them to the
606 class name. For example:
608 use Attribute::Handlers
609 autotie => { Dir => 'Tie::Dir qw(DIR_UNLINK)' };
611 If the attribute name is unqualified, the attribute is installed in the
612 current package. Otherwise it is installed in the qualifier's package:
616 use Attribute::Handlers autotie => {
617 Other::Good => Tie::SecureHash, # tie attr installed in Other::
618 Bad => Tie::Taxes, # tie attr installed in Here::
619 UNIVERSAL::Ugly => Software::Patent # tie attr installed everywhere
622 Autoties are most commonly used in the module to which they actually tie,
623 and need to export their attributes to any module that calls them. To
624 facilitate this, Attribute::Handlers recognizes a special "pseudo-class" --
625 C<__CALLER__>, which may be specified as the qualifier of an attribute:
627 package Tie::Me::Kangaroo:Down::Sport;
629 use Attribute::Handlers autotie => { '__CALLER__::Roo' => __PACKAGE__ };
631 This causes Attribute::Handlers to define the C<Roo> attribute in the package
632 that imports the Tie::Me::Kangaroo:Down::Sport module.
634 Note that it is important to quote the __CALLER__::Roo identifier because
635 a bug in perl 5.8 will refuse to parse it and cause an unknown error.
637 =head3 Passing the tied object to C<tie>
639 Occasionally it is important to pass a reference to the object being tied
640 to the TIESCALAR, TIEHASH, etc. that ties it.
642 The C<autotie> mechanism supports this too. The following code:
644 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
645 my $var : Selfish(@args);
647 has the same effect as:
649 tie my $var, 'Tie::Selfish', @args;
651 But when C<"autotieref"> is used instead of C<"autotie">:
653 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
654 my $var : Selfish(@args);
656 the effect is to pass the C<tie> call an extra reference to the variable
659 tie my $var, 'Tie::Selfish', \$var, @args;
665 If the class shown in L<SYNOPSIS> were placed in the MyClass.pm
666 module, then the following code:
671 my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
673 package SomeOtherClass;
678 sub fn :Ugly(sister) :Omni('po',tent()) {...}
679 my @arr :Good :Omni(s/cie/nt/);
680 my %hsh :Good(q/bye) :Omni(q/bus/);
683 would cause the following handlers to be invoked:
685 # my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
687 MyClass::Good:ATTR(SCALAR)( 'MyClass', # class
688 'LEXICAL', # no typeglob
692 'CHECK', # compiler phase
695 MyClass::Bad:ATTR(SCALAR)( 'MyClass', # class
696 'LEXICAL', # no typeglob
700 'CHECK', # compiler phase
703 MyClass::Omni:ATTR(SCALAR)( 'MyClass', # class
704 'LEXICAL', # no typeglob
707 '-vorous' # eval'd attr data
708 'CHECK', # compiler phase
712 # sub fn :Ugly(sister) :Omni('po',tent()) {...}
714 MyClass::UGLY:ATTR(CODE)( 'SomeOtherClass', # class
715 \*SomeOtherClass::fn, # typeglob
716 \&SomeOtherClass::fn, # referent
718 'sister' # eval'd attr data
719 'CHECK', # compiler phase
722 MyClass::Omni:ATTR(CODE)( 'SomeOtherClass', # class
723 \*SomeOtherClass::fn, # typeglob
724 \&SomeOtherClass::fn, # referent
726 ['po','acle'] # eval'd attr data
727 'CHECK', # compiler phase
731 # my @arr :Good :Omni(s/cie/nt/);
733 MyClass::Good:ATTR(ARRAY)( 'SomeOtherClass', # class
734 'LEXICAL', # no typeglob
738 'CHECK', # compiler phase
741 MyClass::Omni:ATTR(ARRAY)( 'SomeOtherClass', # class
742 'LEXICAL', # no typeglob
745 "" # eval'd attr data
746 'CHECK', # compiler phase
750 # my %hsh :Good(q/bye) :Omni(q/bus/);
752 MyClass::Good:ATTR(HASH)( 'SomeOtherClass', # class
753 'LEXICAL', # no typeglob
756 'q/bye' # raw attr data
757 'CHECK', # compiler phase
760 MyClass::Omni:ATTR(HASH)( 'SomeOtherClass', # class
761 'LEXICAL', # no typeglob
764 'bus' # eval'd attr data
765 'CHECK', # compiler phase
769 Installing handlers into UNIVERSAL, makes them...err..universal.
772 package Descriptions;
773 use Attribute::Handlers;
776 sub name { return $name{$_[2]}||*{$_[1]}{NAME} }
778 sub UNIVERSAL::Name :ATTR {
779 $name{$_[2]} = $_[4];
782 sub UNIVERSAL::Purpose :ATTR {
783 print STDERR "Purpose of ", &name, " is $_[4]\n";
786 sub UNIVERSAL::Unit :ATTR {
787 print STDERR &name, " measured in $_[4]\n";
794 my $capacity : Name(capacity)
795 : Purpose(to store max storage capacity for files)
801 sub foo : Purpose(to foo all data before barring it) { }
810 =item C<Bad attribute type: ATTR(%s)>
812 An attribute handler was specified with an C<:ATTR(I<ref_type>)>, but the
813 type of referent it was defined to handle wasn't one of the five permitted:
814 C<SCALAR>, C<ARRAY>, C<HASH>, C<CODE>, or C<ANY>.
816 =item C<Attribute handler %s doesn't handle %s attributes>
818 A handler for attributes of the specified name I<was> defined, but not
819 for the specified type of declaration. Typically encountered whe trying
820 to apply a C<VAR> attribute handler to a subroutine, or a C<SCALAR>
821 attribute handler to some other type of variable.
823 =item C<Declaration of %s attribute in package %s may clash with future reserved word>
825 A handler for an attributes with an all-lowercase name was declared. An
826 attribute with an all-lowercase name might have a meaning to Perl
827 itself some day, even though most don't yet. Use a mixed-case attribute
830 =item C<Can't have two ATTR specifiers on one subroutine>
832 You just can't, okay?
833 Instead, put all the specifications together with commas between them
834 in a single C<ATTR(I<specification>)>.
836 =item C<Can't autotie a %s>
838 You can only declare autoties for types C<"SCALAR">, C<"ARRAY">, and
839 C<"HASH">. They're the only things (apart from typeglobs -- which are
840 not declarable) that Perl can tie.
842 =item C<Internal error: %s symbol went missing>
844 Something is rotten in the state of the program. An attributed
845 subroutine ceased to exist between the point it was declared and the point
846 at which its attribute handler(s) would have been called.
848 =item C<Won't be able to apply END handler>
850 You have defined an END handler for an attribute that is being applied
851 to a lexical variable. Since the variable may not be available during END
858 Damian Conway (damian@conway.org)
862 There are undoubtedly serious bugs lurking somewhere in code this funky :-)
863 Bug reports and other feedback are most welcome.
867 Copyright (c) 2001, Damian Conway. All Rights Reserved.
868 This module is free software. It may be used, redistributed
869 and/or modified under the same terms as Perl itself.