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';
197 $data = !$raw && eval("package $pkg; no warnings; no strict;
198 local \$SIG{__WARN__}=sub{die}; [$data]");
199 if (my $error = $@) {
200 $error =~ s{\s+ at \s+ \(eval \s+ \S+\) \s+ line \s+ \S+}{}x;
201 die "Bad data for $attr attribute: $error\n";
205 (ref $sym eq 'GLOB' ? *{$sym}{ref $ref}||$ref : $ref),
207 (@$data>1? $data : $data->[0]),
220 _apply_handler_AH_($_,'CHECK') foreach @declarations;
225 _apply_handler_AH_($_,'INIT') foreach @declarations
229 END { $global_phase++; _apply_handler_AH_($_,'END') foreach @declarations }
236 Attribute::Handlers - Simpler definition of attribute handlers
240 This document describes version 0.79 of Attribute::Handlers,
241 released November 25, 2007.
247 use Attribute::Handlers;
248 no warnings 'redefine';
251 sub Good : ATTR(SCALAR) {
252 my ($package, $symbol, $referent, $attr, $data) = @_;
254 # Invoked for any scalar variable with a :Good attribute,
255 # provided the variable was declared in MyClass (or
256 # a derived class) or typed to MyClass.
258 # Do whatever to $referent here (executed in CHECK phase).
262 sub Bad : ATTR(SCALAR) {
263 # Invoked for any scalar variable with a :Bad attribute,
264 # provided the variable was declared in MyClass (or
265 # a derived class) or typed to MyClass.
269 sub Good : ATTR(ARRAY) {
270 # Invoked for any array variable with a :Good attribute,
271 # provided the variable was declared in MyClass (or
272 # a derived class) or typed to MyClass.
276 sub Good : ATTR(HASH) {
277 # Invoked for any hash variable with a :Good attribute,
278 # provided the variable was declared in MyClass (or
279 # a derived class) or typed to MyClass.
283 sub Ugly : ATTR(CODE) {
284 # Invoked for any subroutine declared in MyClass (or a
285 # derived class) with an :Ugly attribute.
290 # Invoked for any scalar, array, hash, or subroutine
291 # with an :Omni attribute, provided the variable or
292 # subroutine was declared in MyClass (or a derived class)
293 # or the variable was typed to MyClass.
294 # Use ref($_[2]) to determine what kind of referent it was.
299 use Attribute::Handlers autotie => { Cycle => Tie::Cycle };
301 my $next : Cycle(['A'..'Z']);
306 This module, when inherited by a package, allows that package's class to
307 define attribute handler subroutines for specific attributes. Variables
308 and subroutines subsequently defined in that package, or in packages
309 derived from that package may be given attributes with the same names as
310 the attribute handler subroutines, which will then be called in one of
311 the compilation phases (i.e. in a C<BEGIN>, C<CHECK>, C<INIT>, or C<END>
312 block). (C<UNITCHECK> blocks don't correspond to a global compilation
313 phase, so they can't be specified here.)
315 To create a handler, define it as a subroutine with the same name as
316 the desired attribute, and declare the subroutine itself with the
317 attribute C<:ATTR>. For example:
320 use Attribute::Handlers;
323 my ($package, $symbol, $referent, $attr, $data, $phase, $filename, $linenum) = @_;
326 *{$symbol}{NAME}, " ",
327 "($referent) ", "was just declared ",
328 "and ascribed the ${attr} attribute ",
329 "with data ($data)\n",
331 "in file $filename at line $linenum\n";
334 This creates a handler for the attribute C<:Loud> in the class LoudDecl.
335 Thereafter, any subroutine declared with a C<:Loud> attribute in the class
342 causes the above handler to be invoked, and passed:
348 the name of the package into which it was declared;
352 a reference to the symbol table entry (typeglob) containing the subroutine;
356 a reference to the subroutine;
360 the name of the attribute;
364 any data associated with that attribute;
368 the name of the phase in which the handler is being invoked;
372 the filename in which the handler is being invoked;
376 the line number in this file.
380 Likewise, declaring any variables with the C<:Loud> attribute within the
389 will cause the handler to be called with a similar argument list (except,
390 of course, that C<$_[2]> will be a reference to the variable).
392 The package name argument will typically be the name of the class into
393 which the subroutine was declared, but it may also be the name of a derived
394 class (since handlers are inherited).
396 If a lexical variable is given an attribute, there is no symbol table to
397 which it belongs, so the symbol table argument (C<$_[1]>) is set to the
398 string C<'LEXICAL'> in that case. Likewise, ascribing an attribute to
399 an anonymous subroutine results in a symbol table argument of C<'ANON'>.
401 The data argument passes in the value (if any) associated with the
402 attribute. For example, if C<&foo> had been declared:
404 sub foo :Loud("turn it up to 11, man!") {...}
406 then the string C<"turn it up to 11, man!"> would be passed as the
409 Attribute::Handlers makes strenuous efforts to convert
410 the data argument (C<$_[4]>) to a useable form before passing it to
411 the handler (but see L<"Non-interpretive attribute handlers">).
412 For example, all of these:
414 sub foo :Loud(till=>ears=>are=>bleeding) {...}
415 sub foo :Loud(['till','ears','are','bleeding']) {...}
416 sub foo :Loud(qw/till ears are bleeding/) {...}
417 sub foo :Loud(qw/my, ears, are, bleeding/) {...}
418 sub foo :Loud(till,ears,are,bleeding) {...}
420 causes it to pass C<['till','ears','are','bleeding']> as the handler's
421 data argument. However, if the data can't be parsed as valid Perl, then
422 it is passed as an uninterpreted string. For example:
424 sub foo :Loud(my,ears,are,bleeding) {...}
425 sub foo :Loud(qw/my ears are bleeding) {...}
427 cause the strings C<'my,ears,are,bleeding'> and C<'qw/my ears are bleeding'>
428 respectively to be passed as the data argument.
430 If the attribute has only a single associated scalar data value, that value is
431 passed as a scalar. If multiple values are associated, they are passed as an
432 array reference. If no value is associated with the attribute, C<undef> is
436 =head2 Typed lexicals
438 Regardless of the package in which it is declared, if a lexical variable is
439 ascribed an attribute, the handler that is invoked is the one belonging to
440 the package to which it is typed. For example, the following declarations:
444 my LoudDecl $loudobj : Loud;
445 my LoudDecl @loudobjs : Loud;
446 my LoudDecl %loudobjex : Loud;
448 causes the LoudDecl::Loud handler to be invoked (even if OtherClass also
449 defines a handler for C<:Loud> attributes).
452 =head2 Type-specific attribute handlers
454 If an attribute handler is declared and the C<:ATTR> specifier is
455 given the name of a built-in type (C<SCALAR>, C<ARRAY>, C<HASH>, or C<CODE>),
456 the handler is only applied to declarations of that type. For example,
457 the following definition:
461 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
463 creates an attribute handler that applies only to scalars:
469 my $metal : RealLoud; # invokes &LoudDecl::RealLoud
470 my @metal : RealLoud; # error: unknown attribute
471 my %metal : RealLoud; # error: unknown attribute
472 sub metal : RealLoud {...} # error: unknown attribute
474 You can, of course, declare separate handlers for these types as well
475 (but you'll need to specify C<no warnings 'redefine'> to do it quietly):
478 use Attribute::Handlers;
479 no warnings 'redefine';
481 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
482 sub RealLoud :ATTR(ARRAY) { print "Urrrrrrrrrr!" }
483 sub RealLoud :ATTR(HASH) { print "Arrrrrgggghhhhhh!" }
484 sub RealLoud :ATTR(CODE) { croak "Real loud sub torpedoed" }
486 You can also explicitly indicate that a single handler is meant to be
487 used for all types of referents like so:
490 use Attribute::Handlers;
492 sub SeriousLoud :ATTR(ANY) { warn "Hearing loss imminent" }
494 (I.e. C<ATTR(ANY)> is a synonym for C<:ATTR>).
497 =head2 Non-interpretive attribute handlers
499 Occasionally the strenuous efforts Attribute::Handlers makes to convert
500 the data argument (C<$_[4]>) to a useable form before passing it to
501 the handler get in the way.
503 You can turn off that eagerness-to-help by declaring
504 an attribute handler with the keyword C<RAWDATA>. For example:
506 sub Raw : ATTR(RAWDATA) {...}
507 sub Nekkid : ATTR(SCALAR,RAWDATA) {...}
508 sub Au::Naturale : ATTR(RAWDATA,ANY) {...}
510 Then the handler makes absolutely no attempt to interpret the data it
511 receives and simply passes it as a string:
513 my $power : Raw(1..100); # handlers receives "1..100"
515 =head2 Phase-specific attribute handlers
517 By default, attribute handlers are called at the end of the compilation
518 phase (in a C<CHECK> block). This seems to be optimal in most cases because
519 most things that can be defined are defined by that point but nothing has
522 However, it is possible to set up attribute handlers that are called at
523 other points in the program's compilation or execution, by explicitly
524 stating the phase (or phases) in which you wish the attribute handler to
525 be called. For example:
527 sub Early :ATTR(SCALAR,BEGIN) {...}
528 sub Normal :ATTR(SCALAR,CHECK) {...}
529 sub Late :ATTR(SCALAR,INIT) {...}
530 sub Final :ATTR(SCALAR,END) {...}
531 sub Bookends :ATTR(SCALAR,BEGIN,END) {...}
533 As the last example indicates, a handler may be set up to be (re)called in
534 two or more phases. The phase name is passed as the handler's final argument.
536 Note that attribute handlers that are scheduled for the C<BEGIN> phase
537 are handled as soon as the attribute is detected (i.e. before any
538 subsequently defined C<BEGIN> blocks are executed).
541 =head2 Attributes as C<tie> interfaces
543 Attributes make an excellent and intuitive interface through which to tie
544 variables. For example:
546 use Attribute::Handlers;
549 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
550 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
551 $data = [ $data ] unless ref $data eq 'ARRAY';
552 tie $$referent, 'Tie::Cycle', $data;
559 my $next : Cycle('A'..'Z'); # $next is now a tied variable
565 Note that, because the C<Cycle> attribute receives its arguments in the
566 C<$data> variable, if the attribute is given a list of arguments, C<$data>
567 will consist of a single array reference; otherwise, it will consist of the
568 single argument directly. Since Tie::Cycle requires its cycling values to
569 be passed as an array reference, this means that we need to wrap
570 non-array-reference arguments in an array constructor:
572 $data = [ $data ] unless ref $data eq 'ARRAY';
574 Typically, however, things are the other way around: the tieable class expects
575 its arguments as a flattened list, so the attribute looks like:
577 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
578 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
579 my @data = ref $data eq 'ARRAY' ? @$data : $data;
580 tie $$referent, 'Tie::Whatever', @data;
584 This software pattern is so widely applicable that Attribute::Handlers
585 provides a way to automate it: specifying C<'autotie'> in the
586 C<use Attribute::Handlers> statement. So, the cycling example,
587 could also be written:
589 use Attribute::Handlers autotie => { Cycle => 'Tie::Cycle' };
595 my $next : Cycle(['A'..'Z']); # $next is now a tied variable
600 Note that we now have to pass the cycling values as an array reference,
601 since the C<autotie> mechanism passes C<tie> a list of arguments as a list
602 (as in the Tie::Whatever example), I<not> as an array reference (as in
603 the original Tie::Cycle example at the start of this section).
605 The argument after C<'autotie'> is a reference to a hash in which each key is
606 the name of an attribute to be created, and each value is the class to which
607 variables ascribed that attribute should be tied.
609 Note that there is no longer any need to import the Tie::Cycle module --
610 Attribute::Handlers takes care of that automagically. You can even pass
611 arguments to the module's C<import> subroutine, by appending them to the
612 class name. For example:
614 use Attribute::Handlers
615 autotie => { Dir => 'Tie::Dir qw(DIR_UNLINK)' };
617 If the attribute name is unqualified, the attribute is installed in the
618 current package. Otherwise it is installed in the qualifier's package:
622 use Attribute::Handlers autotie => {
623 Other::Good => Tie::SecureHash, # tie attr installed in Other::
624 Bad => Tie::Taxes, # tie attr installed in Here::
625 UNIVERSAL::Ugly => Software::Patent # tie attr installed everywhere
628 Autoties are most commonly used in the module to which they actually tie,
629 and need to export their attributes to any module that calls them. To
630 facilitate this, Attribute::Handlers recognizes a special "pseudo-class" --
631 C<__CALLER__>, which may be specified as the qualifier of an attribute:
633 package Tie::Me::Kangaroo:Down::Sport;
635 use Attribute::Handlers autotie => { '__CALLER__::Roo' => __PACKAGE__ };
637 This causes Attribute::Handlers to define the C<Roo> attribute in the package
638 that imports the Tie::Me::Kangaroo:Down::Sport module.
640 Note that it is important to quote the __CALLER__::Roo identifier because
641 a bug in perl 5.8 will refuse to parse it and cause an unknown error.
643 =head3 Passing the tied object to C<tie>
645 Occasionally it is important to pass a reference to the object being tied
646 to the TIESCALAR, TIEHASH, etc. that ties it.
648 The C<autotie> mechanism supports this too. The following code:
650 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
651 my $var : Selfish(@args);
653 has the same effect as:
655 tie my $var, 'Tie::Selfish', @args;
657 But when C<"autotieref"> is used instead of C<"autotie">:
659 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
660 my $var : Selfish(@args);
662 the effect is to pass the C<tie> call an extra reference to the variable
665 tie my $var, 'Tie::Selfish', \$var, @args;
671 If the class shown in L<SYNOPSIS> were placed in the MyClass.pm
672 module, then the following code:
677 my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
679 package SomeOtherClass;
684 sub fn :Ugly(sister) :Omni('po',tent()) {...}
685 my @arr :Good :Omni(s/cie/nt/);
686 my %hsh :Good(q/bye) :Omni(q/bus/);
689 would cause the following handlers to be invoked:
691 # my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
693 MyClass::Good:ATTR(SCALAR)( 'MyClass', # class
694 'LEXICAL', # no typeglob
698 'CHECK', # compiler phase
701 MyClass::Bad:ATTR(SCALAR)( 'MyClass', # class
702 'LEXICAL', # no typeglob
706 'CHECK', # compiler phase
709 MyClass::Omni:ATTR(SCALAR)( 'MyClass', # class
710 'LEXICAL', # no typeglob
713 '-vorous' # eval'd attr data
714 'CHECK', # compiler phase
718 # sub fn :Ugly(sister) :Omni('po',tent()) {...}
720 MyClass::UGLY:ATTR(CODE)( 'SomeOtherClass', # class
721 \*SomeOtherClass::fn, # typeglob
722 \&SomeOtherClass::fn, # referent
724 'sister' # eval'd attr data
725 'CHECK', # compiler phase
728 MyClass::Omni:ATTR(CODE)( 'SomeOtherClass', # class
729 \*SomeOtherClass::fn, # typeglob
730 \&SomeOtherClass::fn, # referent
732 ['po','acle'] # eval'd attr data
733 'CHECK', # compiler phase
737 # my @arr :Good :Omni(s/cie/nt/);
739 MyClass::Good:ATTR(ARRAY)( 'SomeOtherClass', # class
740 'LEXICAL', # no typeglob
744 'CHECK', # compiler phase
747 MyClass::Omni:ATTR(ARRAY)( 'SomeOtherClass', # class
748 'LEXICAL', # no typeglob
751 "" # eval'd attr data
752 'CHECK', # compiler phase
756 # my %hsh :Good(q/bye) :Omni(q/bus/);
758 MyClass::Good:ATTR(HASH)( 'SomeOtherClass', # class
759 'LEXICAL', # no typeglob
762 'q/bye' # raw attr data
763 'CHECK', # compiler phase
766 MyClass::Omni:ATTR(HASH)( 'SomeOtherClass', # class
767 'LEXICAL', # no typeglob
770 'bus' # eval'd attr data
771 'CHECK', # compiler phase
775 Installing handlers into UNIVERSAL, makes them...err..universal.
778 package Descriptions;
779 use Attribute::Handlers;
782 sub name { return $name{$_[2]}||*{$_[1]}{NAME} }
784 sub UNIVERSAL::Name :ATTR {
785 $name{$_[2]} = $_[4];
788 sub UNIVERSAL::Purpose :ATTR {
789 print STDERR "Purpose of ", &name, " is $_[4]\n";
792 sub UNIVERSAL::Unit :ATTR {
793 print STDERR &name, " measured in $_[4]\n";
800 my $capacity : Name(capacity)
801 : Purpose(to store max storage capacity for files)
807 sub foo : Purpose(to foo all data before barring it) { }
816 =item C<Bad attribute type: ATTR(%s)>
818 An attribute handler was specified with an C<:ATTR(I<ref_type>)>, but the
819 type of referent it was defined to handle wasn't one of the five permitted:
820 C<SCALAR>, C<ARRAY>, C<HASH>, C<CODE>, or C<ANY>.
822 =item C<Bad data for %s attribute: %s>
824 The data specified as part of the named attribute wasn't valid Perl.
825 The error message indicates why it didn't compile.
827 =item C<Attribute handler %s doesn't handle %s attributes>
829 A handler for attributes of the specified name I<was> defined, but not
830 for the specified type of declaration. Typically encountered whe trying
831 to apply a C<VAR> attribute handler to a subroutine, or a C<SCALAR>
832 attribute handler to some other type of variable.
834 =item C<Declaration of %s attribute in package %s may clash with future reserved word>
836 A handler for an attributes with an all-lowercase name was declared. An
837 attribute with an all-lowercase name might have a meaning to Perl
838 itself some day, even though most don't yet. Use a mixed-case attribute
841 =item C<Can't have two ATTR specifiers on one subroutine>
843 You just can't, okay?
844 Instead, put all the specifications together with commas between them
845 in a single C<ATTR(I<specification>)>.
847 =item C<Can't autotie a %s>
849 You can only declare autoties for types C<"SCALAR">, C<"ARRAY">, and
850 C<"HASH">. They're the only things (apart from typeglobs -- which are
851 not declarable) that Perl can tie.
853 =item C<Internal error: %s symbol went missing>
855 Something is rotten in the state of the program. An attributed
856 subroutine ceased to exist between the point it was declared and the point
857 at which its attribute handler(s) would have been called.
859 =item C<Won't be able to apply END handler>
861 You have defined an END handler for an attribute that is being applied
862 to a lexical variable. Since the variable may not be available during END
869 Damian Conway (damian@conway.org)
873 There are undoubtedly serious bugs lurking somewhere in code this funky :-)
874 Bug reports and other feedback are most welcome.
878 Copyright (c) 2001, Damian Conway. All Rights Reserved.
879 This module is free software. It may be used, redistributed
880 and/or modified under the same terms as Perl itself.