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}"} = $lastattr{ref};
103 my ($class) = $AUTOLOAD =~ m/(.*)::/g;
104 $AUTOLOAD =~ m/_ATTR_(.*?)_(.*)/ or
105 croak "Can't locate class method '$AUTOLOAD' via package '$class'";
106 croak "Attribute handler '$3' doesn't handle $2 attributes";
111 my $builtin = qr/lvalue|method|locked|unique|shared/;
113 sub _gen_handler_AH_() {
116 my ($pkg, $ref, @attrs) = @_;
118 my ($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}];
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 *{"MODIFY_${_}_ATTRIBUTES"} = _gen_handler_AH_ foreach @{$validtype{ANY}};
169 push @UNIVERSAL::ISA, 'Attribute::Handlers'
170 unless grep /^Attribute::Handlers$/, @UNIVERSAL::ISA;
172 sub _apply_handler_AH_ {
173 my ($declaration, $phase) = @_;
174 my ($pkg, $ref, $attr, $data, $raw, $handlerphase) = @$declaration;
175 return unless $handlerphase->{$phase};
176 # print STDERR "Handling $attr on $ref in $phase with [$data]\n";
178 my $handler = "_ATTR_${type}_${attr}";
179 my $sym = findsym($pkg, $ref);
180 $sym ||= $type eq 'CODE' ? 'ANON' : 'LEXICAL';
182 my $evaled = !$raw && eval("package $pkg; no warnings;
183 local \$SIG{__WARN__}=sub{die}; [$data]");
184 $data = ($evaled && $data =~ /^\s*\[/) ? [$evaled]
185 : ($evaled) ? $evaled
188 (ref $sym eq 'GLOB' ? *{$sym}{ref $ref}||$ref : $ref),
190 (@$data>1? $data : $data->[0]),
201 _apply_handler_AH_($_,'CHECK') foreach @declarations;
206 _apply_handler_AH_($_,'INIT') foreach @declarations
210 END { $global_phase++; _apply_handler_AH_($_,'END') foreach @declarations }
217 Attribute::Handlers - Simpler definition of attribute handlers
221 This document describes version 0.78 of Attribute::Handlers,
222 released October 5, 2002.
228 use Attribute::Handlers;
229 no warnings 'redefine';
232 sub Good : ATTR(SCALAR) {
233 my ($package, $symbol, $referent, $attr, $data) = @_;
235 # Invoked for any scalar variable with a :Good attribute,
236 # provided the variable was declared in MyClass (or
237 # a derived class) or typed to MyClass.
239 # Do whatever to $referent here (executed in CHECK phase).
243 sub Bad : ATTR(SCALAR) {
244 # Invoked for any scalar variable with a :Bad attribute,
245 # provided the variable was declared in MyClass (or
246 # a derived class) or typed to MyClass.
250 sub Good : ATTR(ARRAY) {
251 # Invoked for any array variable with a :Good attribute,
252 # provided the variable was declared in MyClass (or
253 # a derived class) or typed to MyClass.
257 sub Good : ATTR(HASH) {
258 # Invoked for any hash variable with a :Good attribute,
259 # provided the variable was declared in MyClass (or
260 # a derived class) or typed to MyClass.
264 sub Ugly : ATTR(CODE) {
265 # Invoked for any subroutine declared in MyClass (or a
266 # derived class) with an :Ugly attribute.
271 # Invoked for any scalar, array, hash, or subroutine
272 # with an :Omni attribute, provided the variable or
273 # subroutine was declared in MyClass (or a derived class)
274 # or the variable was typed to MyClass.
275 # Use ref($_[2]) to determine what kind of referent it was.
280 use Attribute::Handlers autotie => { Cycle => Tie::Cycle };
282 my $next : Cycle(['A'..'Z']);
287 This module, when inherited by a package, allows that package's class to
288 define attribute handler subroutines for specific attributes. Variables
289 and subroutines subsequently defined in that package, or in packages
290 derived from that package may be given attributes with the same names as
291 the attribute handler subroutines, which will then be called in one of
292 the compilation phases (i.e. in a C<BEGIN>, C<CHECK>, C<INIT>, or C<END>
295 To create a handler, define it as a subroutine with the same name as
296 the desired attribute, and declare the subroutine itself with the
297 attribute C<:ATTR>. For example:
300 use Attribute::Handlers;
303 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
306 *{$symbol}{NAME}, " ",
307 "($referent) ", "was just declared ",
308 "and ascribed the ${attr} attribute ",
309 "with data ($data)\n",
313 This creates a handler for the attribute C<:Loud> in the class LoudDecl.
314 Thereafter, any subroutine declared with a C<:Loud> attribute in the class
321 causes the above handler to be invoked, and passed:
327 the name of the package into which it was declared;
331 a reference to the symbol table entry (typeglob) containing the subroutine;
335 a reference to the subroutine;
339 the name of the attribute;
343 any data associated with that attribute;
347 the name of the phase in which the handler is being invoked.
351 Likewise, declaring any variables with the C<:Loud> attribute within the
360 will cause the handler to be called with a similar argument list (except,
361 of course, that C<$_[2]> will be a reference to the variable).
363 The package name argument will typically be the name of the class into
364 which the subroutine was declared, but it may also be the name of a derived
365 class (since handlers are inherited).
367 If a lexical variable is given an attribute, there is no symbol table to
368 which it belongs, so the symbol table argument (C<$_[1]>) is set to the
369 string C<'LEXICAL'> in that case. Likewise, ascribing an attribute to
370 an anonymous subroutine results in a symbol table argument of C<'ANON'>.
372 The data argument passes in the value (if any) associated with the
373 attribute. For example, if C<&foo> had been declared:
375 sub foo :Loud("turn it up to 11, man!") {...}
377 then the string C<"turn it up to 11, man!"> would be passed as the
380 Attribute::Handlers makes strenuous efforts to convert
381 the data argument (C<$_[4]>) to a useable form before passing it to
382 the handler (but see L<"Non-interpretive attribute handlers">).
383 For example, all of these:
385 sub foo :Loud(till=>ears=>are=>bleeding) {...}
386 sub foo :Loud(['till','ears','are','bleeding']) {...}
387 sub foo :Loud(qw/till ears are bleeding/) {...}
388 sub foo :Loud(qw/my, ears, are, bleeding/) {...}
389 sub foo :Loud(till,ears,are,bleeding) {...}
391 causes it to pass C<['till','ears','are','bleeding']> as the handler's
392 data argument. However, if the data can't be parsed as valid Perl, then
393 it is passed as an uninterpreted string. For example:
395 sub foo :Loud(my,ears,are,bleeding) {...}
396 sub foo :Loud(qw/my ears are bleeding) {...}
398 cause the strings C<'my,ears,are,bleeding'> and C<'qw/my ears are bleeding'>
399 respectively to be passed as the data argument.
401 If the attribute has only a single associated scalar data value, that value is
402 passed as a scalar. If multiple values are associated, they are passed as an
403 array reference. If no value is associated with the attribute, C<undef> is
407 =head2 Typed lexicals
409 Regardless of the package in which it is declared, if a lexical variable is
410 ascribed an attribute, the handler that is invoked is the one belonging to
411 the package to which it is typed. For example, the following declarations:
415 my LoudDecl $loudobj : Loud;
416 my LoudDecl @loudobjs : Loud;
417 my LoudDecl %loudobjex : Loud;
419 causes the LoudDecl::Loud handler to be invoked (even if OtherClass also
420 defines a handler for C<:Loud> attributes).
423 =head2 Type-specific attribute handlers
425 If an attribute handler is declared and the C<:ATTR> specifier is
426 given the name of a built-in type (C<SCALAR>, C<ARRAY>, C<HASH>, or C<CODE>),
427 the handler is only applied to declarations of that type. For example,
428 the following definition:
432 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
434 creates an attribute handler that applies only to scalars:
440 my $metal : RealLoud; # invokes &LoudDecl::RealLoud
441 my @metal : RealLoud; # error: unknown attribute
442 my %metal : RealLoud; # error: unknown attribute
443 sub metal : RealLoud {...} # error: unknown attribute
445 You can, of course, declare separate handlers for these types as well
446 (but you'll need to specify C<no warnings 'redefine'> to do it quietly):
449 use Attribute::Handlers;
450 no warnings 'redefine';
452 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
453 sub RealLoud :ATTR(ARRAY) { print "Urrrrrrrrrr!" }
454 sub RealLoud :ATTR(HASH) { print "Arrrrrgggghhhhhh!" }
455 sub RealLoud :ATTR(CODE) { croak "Real loud sub torpedoed" }
457 You can also explicitly indicate that a single handler is meant to be
458 used for all types of referents like so:
461 use Attribute::Handlers;
463 sub SeriousLoud :ATTR(ANY) { warn "Hearing loss imminent" }
465 (I.e. C<ATTR(ANY)> is a synonym for C<:ATTR>).
468 =head2 Non-interpretive attribute handlers
470 Occasionally the strenuous efforts Attribute::Handlers makes to convert
471 the data argument (C<$_[4]>) to a useable form before passing it to
472 the handler get in the way.
474 You can turn off that eagerness-to-help by declaring
475 an attribute handler with the keyword C<RAWDATA>. For example:
477 sub Raw : ATTR(RAWDATA) {...}
478 sub Nekkid : ATTR(SCALAR,RAWDATA) {...}
479 sub Au::Naturale : ATTR(RAWDATA,ANY) {...}
481 Then the handler makes absolutely no attempt to interpret the data it
482 receives and simply passes it as a string:
484 my $power : Raw(1..100); # handlers receives "1..100"
486 =head2 Phase-specific attribute handlers
488 By default, attribute handlers are called at the end of the compilation
489 phase (in a C<CHECK> block). This seems to be optimal in most cases because
490 most things that can be defined are defined by that point but nothing has
493 However, it is possible to set up attribute handlers that are called at
494 other points in the program's compilation or execution, by explicitly
495 stating the phase (or phases) in which you wish the attribute handler to
496 be called. For example:
498 sub Early :ATTR(SCALAR,BEGIN) {...}
499 sub Normal :ATTR(SCALAR,CHECK) {...}
500 sub Late :ATTR(SCALAR,INIT) {...}
501 sub Final :ATTR(SCALAR,END) {...}
502 sub Bookends :ATTR(SCALAR,BEGIN,END) {...}
504 As the last example indicates, a handler may be set up to be (re)called in
505 two or more phases. The phase name is passed as the handler's final argument.
507 Note that attribute handlers that are scheduled for the C<BEGIN> phase
508 are handled as soon as the attribute is detected (i.e. before any
509 subsequently defined C<BEGIN> blocks are executed).
512 =head2 Attributes as C<tie> interfaces
514 Attributes make an excellent and intuitive interface through which to tie
515 variables. For example:
517 use Attribute::Handlers;
520 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
521 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
522 $data = [ $data ] unless ref $data eq 'ARRAY';
523 tie $$referent, 'Tie::Cycle', $data;
530 my $next : Cycle('A'..'Z'); # $next is now a tied variable
536 Note that, because the C<Cycle> attribute receives its arguments in the
537 C<$data> variable, if the attribute is given a list of arguments, C<$data>
538 will consist of a single array reference; otherwise, it will consist of the
539 single argument directly. Since Tie::Cycle requires its cycling values to
540 be passed as an array reference, this means that we need to wrap
541 non-array-reference arguments in an array constructor:
543 $data = [ $data ] unless ref $data eq 'ARRAY';
545 Typically, however, things are the other way around: the tieable class expects
546 its arguments as a flattened list, so the attribute looks like:
548 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
549 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
550 my @data = ref $data eq 'ARRAY' ? @$data : $data;
551 tie $$referent, 'Tie::Whatever', @data;
555 This software pattern is so widely applicable that Attribute::Handlers
556 provides a way to automate it: specifying C<'autotie'> in the
557 C<use Attribute::Handlers> statement. So, the cycling example,
558 could also be written:
560 use Attribute::Handlers autotie => { Cycle => 'Tie::Cycle' };
566 my $next : Cycle(['A'..'Z']); # $next is now a tied variable
571 Note that we now have to pass the cycling values as an array reference,
572 since the C<autotie> mechanism passes C<tie> a list of arguments as a list
573 (as in the Tie::Whatever example), I<not> as an array reference (as in
574 the original Tie::Cycle example at the start of this section).
576 The argument after C<'autotie'> is a reference to a hash in which each key is
577 the name of an attribute to be created, and each value is the class to which
578 variables ascribed that attribute should be tied.
580 Note that there is no longer any need to import the Tie::Cycle module --
581 Attribute::Handlers takes care of that automagically. You can even pass
582 arguments to the module's C<import> subroutine, by appending them to the
583 class name. For example:
585 use Attribute::Handlers
586 autotie => { Dir => 'Tie::Dir qw(DIR_UNLINK)' };
588 If the attribute name is unqualified, the attribute is installed in the
589 current package. Otherwise it is installed in the qualifier's package:
593 use Attribute::Handlers autotie => {
594 Other::Good => Tie::SecureHash, # tie attr installed in Other::
595 Bad => Tie::Taxes, # tie attr installed in Here::
596 UNIVERSAL::Ugly => Software::Patent # tie attr installed everywhere
599 Autoties are most commonly used in the module to which they actually tie,
600 and need to export their attributes to any module that calls them. To
601 facilitiate this, Attribute::Handlers recognizes a special "pseudo-class" --
602 C<__CALLER__>, which may be specified as the qualifier of an attribute:
604 package Tie::Me::Kangaroo:Down::Sport;
606 use Attribute::Handlers autotie => { '__CALLER__::Roo' => __PACKAGE__ };
608 This causes Attribute::Handlers to define the C<Roo> attribute in the package
609 that imports the Tie::Me::Kangaroo:Down::Sport module.
611 Note that it is important to quote the __CALLER__::Roo identifier because
612 a bug in perl 5.8 will refuse to parse it and cause an unknown error.
614 =head3 Passing the tied object to C<tie>
616 Occasionally it is important to pass a reference to the object being tied
617 to the TIESCALAR, TIEHASH, etc. that ties it.
619 The C<autotie> mechanism supports this too. The following code:
621 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
622 my $var : Selfish(@args);
624 has the same effect as:
626 tie my $var, 'Tie::Selfish', @args;
628 But when C<"autotieref"> is used instead of C<"autotie">:
630 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
631 my $var : Selfish(@args);
633 the effect is to pass the C<tie> call an extra reference to the variable
636 tie my $var, 'Tie::Selfish', \$var, @args;
642 If the class shown in L<SYNOPSIS> were placed in the MyClass.pm
643 module, then the following code:
648 my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
650 package SomeOtherClass;
655 sub fn :Ugly(sister) :Omni('po',tent()) {...}
656 my @arr :Good :Omni(s/cie/nt/);
657 my %hsh :Good(q/bye) :Omni(q/bus/);
660 would cause the following handlers to be invoked:
662 # my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
664 MyClass::Good:ATTR(SCALAR)( 'MyClass', # class
665 'LEXICAL', # no typeglob
669 'CHECK', # compiler phase
672 MyClass::Bad:ATTR(SCALAR)( 'MyClass', # class
673 'LEXICAL', # no typeglob
677 'CHECK', # compiler phase
680 MyClass::Omni:ATTR(SCALAR)( 'MyClass', # class
681 'LEXICAL', # no typeglob
684 '-vorous' # eval'd attr data
685 'CHECK', # compiler phase
689 # sub fn :Ugly(sister) :Omni('po',tent()) {...}
691 MyClass::UGLY:ATTR(CODE)( 'SomeOtherClass', # class
692 \*SomeOtherClass::fn, # typeglob
693 \&SomeOtherClass::fn, # referent
695 'sister' # eval'd attr data
696 'CHECK', # compiler phase
699 MyClass::Omni:ATTR(CODE)( 'SomeOtherClass', # class
700 \*SomeOtherClass::fn, # typeglob
701 \&SomeOtherClass::fn, # referent
703 ['po','acle'] # eval'd attr data
704 'CHECK', # compiler phase
708 # my @arr :Good :Omni(s/cie/nt/);
710 MyClass::Good:ATTR(ARRAY)( 'SomeOtherClass', # class
711 'LEXICAL', # no typeglob
715 'CHECK', # compiler phase
718 MyClass::Omni:ATTR(ARRAY)( 'SomeOtherClass', # class
719 'LEXICAL', # no typeglob
722 "" # eval'd attr data
723 'CHECK', # compiler phase
727 # my %hsh :Good(q/bye) :Omni(q/bus/);
729 MyClass::Good:ATTR(HASH)( 'SomeOtherClass', # class
730 'LEXICAL', # no typeglob
733 'q/bye' # raw attr data
734 'CHECK', # compiler phase
737 MyClass::Omni:ATTR(HASH)( 'SomeOtherClass', # class
738 'LEXICAL', # no typeglob
741 'bus' # eval'd attr data
742 'CHECK', # compiler phase
746 Installing handlers into UNIVERSAL, makes them...err..universal.
749 package Descriptions;
750 use Attribute::Handlers;
753 sub name { return $name{$_[2]}||*{$_[1]}{NAME} }
755 sub UNIVERSAL::Name :ATTR {
756 $name{$_[2]} = $_[4];
759 sub UNIVERSAL::Purpose :ATTR {
760 print STDERR "Purpose of ", &name, " is $_[4]\n";
763 sub UNIVERSAL::Unit :ATTR {
764 print STDERR &name, " measured in $_[4]\n";
771 my $capacity : Name(capacity)
772 : Purpose(to store max storage capacity for files)
778 sub foo : Purpose(to foo all data before barring it) { }
787 =item C<Bad attribute type: ATTR(%s)>
789 An attribute handler was specified with an C<:ATTR(I<ref_type>)>, but the
790 type of referent it was defined to handle wasn't one of the five permitted:
791 C<SCALAR>, C<ARRAY>, C<HASH>, C<CODE>, or C<ANY>.
793 =item C<Attribute handler %s doesn't handle %s attributes>
795 A handler for attributes of the specified name I<was> defined, but not
796 for the specified type of declaration. Typically encountered whe trying
797 to apply a C<VAR> attribute handler to a subroutine, or a C<SCALAR>
798 attribute handler to some other type of variable.
800 =item C<Declaration of %s attribute in package %s may clash with future reserved word>
802 A handler for an attributes with an all-lowercase name was declared. An
803 attribute with an all-lowercase name might have a meaning to Perl
804 itself some day, even though most don't yet. Use a mixed-case attribute
807 =item C<Can't have two ATTR specifiers on one subroutine>
809 You just can't, okay?
810 Instead, put all the specifications together with commas between them
811 in a single C<ATTR(I<specification>)>.
813 =item C<Can't autotie a %s>
815 You can only declare autoties for types C<"SCALAR">, C<"ARRAY">, and
816 C<"HASH">. They're the only things (apart from typeglobs -- which are
817 not declarable) that Perl can tie.
819 =item C<Internal error: %s symbol went missing>
821 Something is rotten in the state of the program. An attributed
822 subroutine ceased to exist between the point it was declared and the point
823 at which its attribute handler(s) would have been called.
825 =item C<Won't be able to apply END handler>
827 You have defined an END handler for an attribute that is being applied
828 to a lexical variable. Since the variable may not be available during END
835 Damian Conway (damian@conway.org)
839 There are undoubtedly serious bugs lurking somewhere in code this funky :-)
840 Bug reports and other feedback are most welcome.
844 Copyright (c) 2001, Damian Conway. All Rights Reserved.
845 This module is free software. It may be used, redistributed
846 and/or modified under the same terms as Perl itself.