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 $builtin = qr/lvalue|method|locked/;
113 sub _gen_handler_AH_() {
116 my ($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);
140 my $handler = $pkg->can($attr);
141 next unless $handler;
142 my $decl = [$pkg, $ref, $attr, $data,
143 $raw{$handler}, $phase{$handler}];
144 foreach my $gphase (@global_phases) {
145 _apply_handler_AH_($decl,$gphase)
146 if $global_phases{$gphase} <= $global_phase;
148 if ($global_phase != 0) {
149 # if _gen_handler_AH_ is being called after
150 # CHECK it's for a lexical, so make sure
151 # it didn't want to run anything later
153 local $Carp::CarpLevel = 2;
154 carp "Won't be able to apply END handler"
155 if $phase{$handler}{END};
158 push @declarations, $decl
163 return grep {defined && !/$builtin/} @attrs;
167 *{"MODIFY_${_}_ATTRIBUTES"} = _gen_handler_AH_ foreach @{$validtype{ANY}};
168 push @UNIVERSAL::ISA, 'Attribute::Handlers'
169 unless grep /^Attribute::Handlers$/, @UNIVERSAL::ISA;
171 sub _apply_handler_AH_ {
172 my ($declaration, $phase) = @_;
173 my ($pkg, $ref, $attr, $data, $raw, $handlerphase) = @$declaration;
174 return unless $handlerphase->{$phase};
175 # print STDERR "Handling $attr on $ref in $phase with [$data]\n";
177 my $handler = "_ATTR_${type}_${attr}";
178 my $sym = findsym($pkg, $ref);
179 $sym ||= $type eq 'CODE' ? 'ANON' : 'LEXICAL';
181 my $evaled = !$raw && eval("package $pkg; no warnings;
182 local \$SIG{__WARN__}=sub{die}; [$data]");
183 $data = ($evaled && $data =~ /^\s*\[/) ? [$evaled]
184 : ($evaled) ? $evaled
187 (ref $sym eq 'GLOB' ? *{$sym}{ref $ref}||$ref : $ref),
189 (@$data>1? $data : $data->[0]),
198 _apply_handler_AH_($_,'CHECK') foreach @declarations;
201 INIT { $global_phase++; _apply_handler_AH_($_,'INIT') foreach @declarations }
203 END { $global_phase++; _apply_handler_AH_($_,'END') foreach @declarations }
210 Attribute::Handlers - Simpler definition of attribute handlers
214 This document describes version 0.76 of Attribute::Handlers,
215 released November 15, 2001.
221 use Attribute::Handlers;
222 no warnings 'redefine';
225 sub Good : ATTR(SCALAR) {
226 my ($package, $symbol, $referent, $attr, $data) = @_;
228 # Invoked for any scalar variable with a :Good attribute,
229 # provided the variable was declared in MyClass (or
230 # a derived class) or typed to MyClass.
232 # Do whatever to $referent here (executed in CHECK phase).
236 sub Bad : ATTR(SCALAR) {
237 # Invoked for any scalar variable with a :Bad attribute,
238 # provided the variable was declared in MyClass (or
239 # a derived class) or typed to MyClass.
243 sub Good : ATTR(ARRAY) {
244 # Invoked for any array variable with a :Good attribute,
245 # provided the variable was declared in MyClass (or
246 # a derived class) or typed to MyClass.
250 sub Good : ATTR(HASH) {
251 # Invoked for any hash variable with a :Good attribute,
252 # provided the variable was declared in MyClass (or
253 # a derived class) or typed to MyClass.
257 sub Ugly : ATTR(CODE) {
258 # Invoked for any subroutine declared in MyClass (or a
259 # derived class) with an :Ugly attribute.
264 # Invoked for any scalar, array, hash, or subroutine
265 # with an :Omni attribute, provided the variable or
266 # subroutine was declared in MyClass (or a derived class)
267 # or the variable was typed to MyClass.
268 # Use ref($_[2]) to determine what kind of referent it was.
273 use Attribute::Handlers autotie => { Cycle => Tie::Cycle };
275 my $next : Cycle(['A'..'Z']);
280 This module, when inherited by a package, allows that package's class to
281 define attribute handler subroutines for specific attributes. Variables
282 and subroutines subsequently defined in that package, or in packages
283 derived from that package may be given attributes with the same names as
284 the attribute handler subroutines, which will then be called in one of
285 the compilation phases (i.e. in a C<BEGIN>, C<CHECK>, C<INIT>, or C<END>
288 To create a handler, define it as a subroutine with the same name as
289 the desired attribute, and declare the subroutine itself with the
290 attribute C<:ATTR>. For example:
293 use Attribute::Handlers;
296 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
299 *{$symbol}{NAME}, " ",
300 "($referent) ", "was just declared ",
301 "and ascribed the ${attr} attribute ",
302 "with data ($data)\n",
306 This creates a handler for the attribute C<:Loud> in the class LoudDecl.
307 Thereafter, any subroutine declared with a C<:Loud> attribute in the class
314 causes the above handler to be invoked, and passed:
320 the name of the package into which it was declared;
324 a reference to the symbol table entry (typeglob) containing the subroutine;
328 a reference to the subroutine;
332 the name of the attribute;
336 any data associated with that attribute;
340 the name of the phase in which the handler is being invoked.
344 Likewise, declaring any variables with the C<:Loud> attribute within the
353 will cause the handler to be called with a similar argument list (except,
354 of course, that C<$_[2]> will be a reference to the variable).
356 The package name argument will typically be the name of the class into
357 which the subroutine was declared, but it may also be the name of a derived
358 class (since handlers are inherited).
360 If a lexical variable is given an attribute, there is no symbol table to
361 which it belongs, so the symbol table argument (C<$_[1]>) is set to the
362 string C<'LEXICAL'> in that case. Likewise, ascribing an attribute to
363 an anonymous subroutine results in a symbol table argument of C<'ANON'>.
365 The data argument passes in the value (if any) associated with the
366 attribute. For example, if C<&foo> had been declared:
368 sub foo :Loud("turn it up to 11, man!") {...}
370 then the string C<"turn it up to 11, man!"> would be passed as the
373 Attribute::Handlers makes strenuous efforts to convert
374 the data argument (C<$_[4]>) to a useable form before passing it to
375 the handler (but see L<"Non-interpretive attribute handlers">).
376 For example, all of these:
378 sub foo :Loud(till=>ears=>are=>bleeding) {...}
379 sub foo :Loud(['till','ears','are','bleeding']) {...}
380 sub foo :Loud(qw/till ears are bleeding/) {...}
381 sub foo :Loud(qw/my, ears, are, bleeding/) {...}
382 sub foo :Loud(till,ears,are,bleeding) {...}
384 causes it to pass C<['till','ears','are','bleeding']> as the handler's
385 data argument. However, if the data can't be parsed as valid Perl, then
386 it is passed as an uninterpreted string. For example:
388 sub foo :Loud(my,ears,are,bleeding) {...}
389 sub foo :Loud(qw/my ears are bleeding) {...}
391 cause the strings C<'my,ears,are,bleeding'> and C<'qw/my ears are bleeding'>
392 respectively to be passed as the data argument.
394 If the attribute has only a single associated scalar data value, that value is
395 passed as a scalar. If multiple values are associated, they are passed as an
396 array reference. If no value is associated with the attribute, C<undef> is
400 =head2 Typed lexicals
402 Regardless of the package in which it is declared, if a lexical variable is
403 ascribed an attribute, the handler that is invoked is the one belonging to
404 the package to which it is typed. For example, the following declarations:
408 my LoudDecl $loudobj : Loud;
409 my LoudDecl @loudobjs : Loud;
410 my LoudDecl %loudobjex : Loud;
412 causes the LoudDecl::Loud handler to be invoked (even if OtherClass also
413 defines a handler for C<:Loud> attributes).
416 =head2 Type-specific attribute handlers
418 If an attribute handler is declared and the C<:ATTR> specifier is
419 given the name of a built-in type (C<SCALAR>, C<ARRAY>, C<HASH>, or C<CODE>),
420 the handler is only applied to declarations of that type. For example,
421 the following definition:
425 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
427 creates an attribute handler that applies only to scalars:
433 my $metal : RealLoud; # invokes &LoudDecl::RealLoud
434 my @metal : RealLoud; # error: unknown attribute
435 my %metal : RealLoud; # error: unknown attribute
436 sub metal : RealLoud {...} # error: unknown attribute
438 You can, of course, declare separate handlers for these types as well
439 (but you'll need to specify C<no warnings 'redefine'> to do it quietly):
442 use Attribute::Handlers;
443 no warnings 'redefine';
445 sub RealLoud :ATTR(SCALAR) { print "Yeeeeow!" }
446 sub RealLoud :ATTR(ARRAY) { print "Urrrrrrrrrr!" }
447 sub RealLoud :ATTR(HASH) { print "Arrrrrgggghhhhhh!" }
448 sub RealLoud :ATTR(CODE) { croak "Real loud sub torpedoed" }
450 You can also explicitly indicate that a single handler is meant to be
451 used for all types of referents like so:
454 use Attribute::Handlers;
456 sub SeriousLoud :ATTR(ANY) { warn "Hearing loss imminent" }
458 (I.e. C<ATTR(ANY)> is a synonym for C<:ATTR>).
461 =head2 Non-interpretive attribute handlers
463 Occasionally the strenuous efforts Attribute::Handlers makes to convert
464 the data argument (C<$_[4]>) to a useable form before passing it to
465 the handler get in the way.
467 You can turn off that eagerness-to-help by declaring
468 an attribute handler with the keyword C<RAWDATA>. For example:
470 sub Raw : ATTR(RAWDATA) {...}
471 sub Nekkid : ATTR(SCALAR,RAWDATA) {...}
472 sub Au::Naturale : ATTR(RAWDATA,ANY) {...}
474 Then the handler makes absolutely no attempt to interpret the data it
475 receives and simply passes it as a string:
477 my $power : Raw(1..100); # handlers receives "1..100"
479 =head2 Phase-specific attribute handlers
481 By default, attribute handlers are called at the end of the compilation
482 phase (in a C<CHECK> block). This seems to be optimal in most cases because
483 most things that can be defined are defined by that point but nothing has
486 However, it is possible to set up attribute handlers that are called at
487 other points in the program's compilation or execution, by explicitly
488 stating the phase (or phases) in which you wish the attribute handler to
489 be called. For example:
491 sub Early :ATTR(SCALAR,BEGIN) {...}
492 sub Normal :ATTR(SCALAR,CHECK) {...}
493 sub Late :ATTR(SCALAR,INIT) {...}
494 sub Final :ATTR(SCALAR,END) {...}
495 sub Bookends :ATTR(SCALAR,BEGIN,END) {...}
497 As the last example indicates, a handler may be set up to be (re)called in
498 two or more phases. The phase name is passed as the handler's final argument.
500 Note that attribute handlers that are scheduled for the C<BEGIN> phase
501 are handled as soon as the attribute is detected (i.e. before any
502 subsequently defined C<BEGIN> blocks are executed).
505 =head2 Attributes as C<tie> interfaces
507 Attributes make an excellent and intuitive interface through which to tie
508 variables. For example:
510 use Attribute::Handlers;
513 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
514 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
515 $data = [ $data ] unless ref $data eq 'ARRAY';
516 tie $$referent, 'Tie::Cycle', $data;
523 my $next : Cycle('A'..'Z'); # $next is now a tied variable
529 Note that, because the C<Cycle> attribute receives its arguments in the
530 C<$data> variable, if the attribute is given a list of arguments, C<$data>
531 will consist of a single array reference; otherwise, it will consist of the
532 single argument directly. Since Tie::Cycle requires its cycling values to
533 be passed as an array reference, this means that we need to wrap
534 non-array-reference arguments in an array constructor:
536 $data = [ $data ] unless ref $data eq 'ARRAY';
538 Typically, however, things are the other way around: the tieable class expects
539 its arguments as a flattened list, so the attribute looks like:
541 sub UNIVERSAL::Cycle : ATTR(SCALAR) {
542 my ($package, $symbol, $referent, $attr, $data, $phase) = @_;
543 my @data = ref $data eq 'ARRAY' ? @$data : $data;
544 tie $$referent, 'Tie::Whatever', @data;
548 This software pattern is so widely applicable that Attribute::Handlers
549 provides a way to automate it: specifying C<'autotie'> in the
550 C<use Attribute::Handlers> statement. So, the cycling example,
551 could also be written:
553 use Attribute::Handlers autotie => { Cycle => 'Tie::Cycle' };
559 my $next : Cycle(['A'..'Z']); # $next is now a tied variable
564 Note that we now have to pass the cycling values as an array reference,
565 since the C<autotie> mechanism passes C<tie> a list of arguments as a list
566 (as in the Tie::Whatever example), I<not> as an array reference (as in
567 the original Tie::Cycle example at the start of this section).
569 The argument after C<'autotie'> is a reference to a hash in which each key is
570 the name of an attribute to be created, and each value is the class to which
571 variables ascribed that attribute should be tied.
573 Note that there is no longer any need to import the Tie::Cycle module --
574 Attribute::Handlers takes care of that automagically. You can even pass
575 arguments to the module's C<import> subroutine, by appending them to the
576 class name. For example:
578 use Attribute::Handlers
579 autotie => { Dir => 'Tie::Dir qw(DIR_UNLINK)' };
581 If the attribute name is unqualified, the attribute is installed in the
582 current package. Otherwise it is installed in the qualifier's package:
586 use Attribute::Handlers autotie => {
587 Other::Good => Tie::SecureHash, # tie attr installed in Other::
588 Bad => Tie::Taxes, # tie attr installed in Here::
589 UNIVERSAL::Ugly => Software::Patent # tie attr installed everywhere
592 Autoties are most commonly used in the module to which they actually tie,
593 and need to export their attributes to any module that calls them. To
594 facilitiate this, Attribute::Handlers recognizes a special "pseudo-class" --
595 C<__CALLER__>, which may be specified as the qualifier of an attribute:
597 package Tie::Me::Kangaroo:Down::Sport;
599 use Attribute::Handlers autotie => { __CALLER__::Roo => __PACKAGE__ };
601 This causes Attribute::Handlers to define the C<Roo> attribute in the package
602 that imports the Tie::Me::Kangaroo:Down::Sport module.
604 =head3 Passing the tied object to C<tie>
606 Occasionally it is important to pass a reference to the object being tied
607 to the TIESCALAR, TIEHASH, etc. that ties it.
609 The C<autotie> mechanism supports this too. The following code:
611 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
612 my $var : Selfish(@args);
614 has the same effect as:
616 tie my $var, 'Tie::Selfish', @args;
618 But when C<"autotieref"> is used instead of C<"autotie">:
620 use Attribute::Handlers autotieref => { Selfish => Tie::Selfish };
621 my $var : Selfish(@args);
623 the effect is to pass the C<tie> call an extra reference to the variable
626 tie my $var, 'Tie::Selfish', \$var, @args;
632 If the class shown in L<SYNOPSIS> were placed in the MyClass.pm
633 module, then the following code:
638 my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
640 package SomeOtherClass;
645 sub fn :Ugly(sister) :Omni('po',tent()) {...}
646 my @arr :Good :Omni(s/cie/nt/);
647 my %hsh :Good(q/bye) :Omni(q/bus/);
650 would cause the following handlers to be invoked:
652 # my MyClass $slr :Good :Bad(1**1-1) :Omni(-vorous);
654 MyClass::Good:ATTR(SCALAR)( 'MyClass', # class
655 'LEXICAL', # no typeglob
659 'CHECK', # compiler phase
662 MyClass::Bad:ATTR(SCALAR)( 'MyClass', # class
663 'LEXICAL', # no typeglob
667 'CHECK', # compiler phase
670 MyClass::Omni:ATTR(SCALAR)( 'MyClass', # class
671 'LEXICAL', # no typeglob
674 '-vorous' # eval'd attr data
675 'CHECK', # compiler phase
679 # sub fn :Ugly(sister) :Omni('po',tent()) {...}
681 MyClass::UGLY:ATTR(CODE)( 'SomeOtherClass', # class
682 \*SomeOtherClass::fn, # typeglob
683 \&SomeOtherClass::fn, # referent
685 'sister' # eval'd attr data
686 'CHECK', # compiler phase
689 MyClass::Omni:ATTR(CODE)( 'SomeOtherClass', # class
690 \*SomeOtherClass::fn, # typeglob
691 \&SomeOtherClass::fn, # referent
693 ['po','acle'] # eval'd attr data
694 'CHECK', # compiler phase
698 # my @arr :Good :Omni(s/cie/nt/);
700 MyClass::Good:ATTR(ARRAY)( 'SomeOtherClass', # class
701 'LEXICAL', # no typeglob
705 'CHECK', # compiler phase
708 MyClass::Omni:ATTR(ARRAY)( 'SomeOtherClass', # class
709 'LEXICAL', # no typeglob
712 "" # eval'd attr data
713 'CHECK', # compiler phase
717 # my %hsh :Good(q/bye) :Omni(q/bus/);
719 MyClass::Good:ATTR(HASH)( 'SomeOtherClass', # class
720 'LEXICAL', # no typeglob
723 'q/bye' # raw attr data
724 'CHECK', # compiler phase
727 MyClass::Omni:ATTR(HASH)( 'SomeOtherClass', # class
728 'LEXICAL', # no typeglob
731 'bus' # eval'd attr data
732 'CHECK', # compiler phase
736 Installing handlers into UNIVERSAL, makes them...err..universal.
739 package Descriptions;
740 use Attribute::Handlers;
743 sub name { return $name{$_[2]}||*{$_[1]}{NAME} }
745 sub UNIVERSAL::Name :ATTR {
746 $name{$_[2]} = $_[4];
749 sub UNIVERSAL::Purpose :ATTR {
750 print STDERR "Purpose of ", &name, " is $_[4]\n";
753 sub UNIVERSAL::Unit :ATTR {
754 print STDERR &name, " measured in $_[4]\n";
761 my $capacity : Name(capacity)
762 : Purpose(to store max storage capacity for files)
768 sub foo : Purpose(to foo all data before barring it) { }
777 =item C<Bad attribute type: ATTR(%s)>
779 An attribute handler was specified with an C<:ATTR(I<ref_type>)>, but the
780 type of referent it was defined to handle wasn't one of the five permitted:
781 C<SCALAR>, C<ARRAY>, C<HASH>, C<CODE>, or C<ANY>.
783 =item C<Attribute handler %s doesn't handle %s attributes>
785 A handler for attributes of the specified name I<was> defined, but not
786 for the specified type of declaration. Typically encountered whe trying
787 to apply a C<VAR> attribute handler to a subroutine, or a C<SCALAR>
788 attribute handler to some other type of variable.
790 =item C<Declaration of %s attribute in package %s may clash with future reserved word>
792 A handler for an attributes with an all-lowercase name was declared. An
793 attribute with an all-lowercase name might have a meaning to Perl
794 itself some day, even though most don't yet. Use a mixed-case attribute
797 =item C<Can't have two ATTR specifiers on one subroutine>
799 You just can't, okay?
800 Instead, put all the specifications together with commas between them
801 in a single C<ATTR(I<specification>)>.
803 =item C<Can't autotie a %s>
805 You can only declare autoties for types C<"SCALAR">, C<"ARRAY">, and
806 C<"HASH">. They're the only things (apart from typeglobs -- which are
807 not declarable) that Perl can tie.
809 =item C<Internal error: %s symbol went missing>
811 Something is rotten in the state of the program. An attributed
812 subroutine ceased to exist between the point it was declared and the point
813 at which its attribute handler(s) would have been called.
815 =item C<Won't be able to apply END handler>
817 You have defined an END handler for an attribute that is being applied
818 to a lexical variable. Since the variable may not be available during END
825 Damian Conway (damian@conway.org)
829 There are undoubtedly serious bugs lurking somewhere in code this funky :-)
830 Bug reports and other feedback are most welcome.
834 Copyright (c) 2001, Damian Conway. All Rights Reserved.
835 This module is free software. It may be used, redistributed
836 and/or modified under the same terms as Perl itself.