FM / pod

/usr/share/perl5/pod

Name	Size	Mode	Actions
perl.pod	16270	0644	edit dl rm
perl56delta.pod	107201	0644	edit dl rm
perl58delta.pod	115165	0644	edit dl rm
perl561delta.pod	124713	0644	edit dl rm
perl581delta.pod	38061	0644	edit dl rm
perl582delta.pod	4470	0644	edit dl rm
perl583delta.pod	6335	0644	edit dl rm
perl584delta.pod	7363	0644	edit dl rm
perl585delta.pod	5889	0644	edit dl rm
perl586delta.pod	4651	0644	edit dl rm
perl587delta.pod	8357	0644	edit dl rm
perl588delta.pod	25272	0644	edit dl rm
perl589delta.pod	53900	0644	edit dl rm
perl5004delta.pod	56240	0644	edit dl rm
perl5005delta.pod	34283	0644	edit dl rm
perl5100delta.pod	55535	0644	edit dl rm
perl5101delta.pod	43888	0644	edit dl rm
perl5120delta.pod	89272	0644	edit dl rm
perl5121delta.pod	10141	0644	edit dl rm
perl5122delta.pod	9603	0644	edit dl rm
perl5123delta.pod	4100	0644	edit dl rm
perl5124delta.pod	3672	0644	edit dl rm
perl5125delta.pod	7683	0644	edit dl rm
perl5140delta.pod	144324	0644	edit dl rm
perl5141delta.pod	7966	0644	edit dl rm
perl5142delta.pod	6892	0644	edit dl rm
perl5143delta.pod	7760	0644	edit dl rm
perl5144delta.pod	6327	0644	edit dl rm
perl5160delta.pod	133651	0644	edit dl rm
perl5161delta.pod	6142	0644	edit dl rm
perl5162delta.pod	3594	0644	edit dl rm
perl5163delta.pod	4085	0644	edit dl rm
perl5180delta.pod	119431	0644	edit dl rm
perl5181delta.pod	6595	0644	edit dl rm
perl5182delta.pod	5335	0644	edit dl rm
perl5184delta.pod	4642	0644	edit dl rm
perl5200delta.pod	115699	0644	edit dl rm
perl5201delta.pod	10899	0644	edit dl rm
perl5202delta.pod	12509	0644	edit dl rm
perl5203delta.pod	9392	0644	edit dl rm
perl5220delta.pod	130963	0644	edit dl rm
perl5221delta.pod	10767	0644	edit dl rm
perl5222delta.pod	12629	0644	edit dl rm
perl5223delta.pod	8456	0644	edit dl rm
perl5224delta.pod	4460	0644	edit dl rm
perl5240delta.pod	64927	0644	edit dl rm
perl5241delta.pod	8215	0644	edit dl rm
perl5242delta.pod	4113	0644	edit dl rm
perl5243delta.pod	11428	0644	edit dl rm
perl5244delta.pod	4510	0644	edit dl rm
perl5260delta.pod	101836	0644	edit dl rm
perl5261delta.pod	7927	0644	edit dl rm
perl5262delta.pod	7880	0644	edit dl rm
perl5263delta.pod	7063	0644	edit dl rm
perl5280delta.pod	72113	0644	edit dl rm
perlaix.pod	20437	0644	edit dl rm
perlamiga.pod	5749	0644	edit dl rm
perlandroid.pod	7871	0644	edit dl rm
perlapi.pod	443535	0644	edit dl rm
perlapio.pod	19285	0644	edit dl rm
perlartistic.pod	7010	0644	edit dl rm
perlbook.pod	8338	0644	edit dl rm
perlboot.pod	294	0644	edit dl rm
perlbot.pod	304	0644	edit dl rm
perlbs2000.pod	8058	0644	edit dl rm
perlcall.pod	56706	0644	edit dl rm
perlce.pod	14602	0644	edit dl rm
perlcheat.pod	4481	0644	edit dl rm
perlclib.pod	9619	0644	edit dl rm
perlcn.pod	4691	0644	edit dl rm
perlcommunity.pod	7217	0644	edit dl rm
perlcygwin.pod	27199	0644	edit dl rm
perldata.pod	46743	0644	edit dl rm
perldbmfilter.pod	4981	0644	edit dl rm
perldebguts.pod	38535	0644	edit dl rm
perldebtut.pod	22152	0644	edit dl rm
perldebug.pod	39258	0644	edit dl rm
perldelta.pod	7063	0644	edit dl rm
perldeprecation.pod	18169	0644	edit dl rm
perldiag.pod	284572	0644	edit dl rm
perldos.pod	10522	0644	edit dl rm
perldsc.pod	25614	0644	edit dl rm
perldtrace.pod	7958	0644	edit dl rm
perlebcdic.pod	84233	0644	edit dl rm
perlembed.pod	37196	0644	edit dl rm
perlexperiment.pod	7195	0644	edit dl rm
perlfork.pod	13355	0644	edit dl rm
perlform.pod	16608	0644	edit dl rm
perlfreebsd.pod	1610	0644	edit dl rm
perlfunc.pod	392957	0644	edit dl rm
perlgit.pod	33509	0644	edit dl rm
perlgpl.pod	13815	0644	edit dl rm
perlguts.pod	139329	0644	edit dl rm
perlhack.pod	40445	0644	edit dl rm
perlhacktips.pod	55509	0644	edit dl rm
perlhacktut.pod	6153	0644	edit dl rm
perlhaiku.pod	1508	0644	edit dl rm
perlhist.pod	53546	0644	edit dl rm
perlhpux.pod	30509	0644	edit dl rm
perlhurd.pod	1993	0644	edit dl rm
perlintern.pod	54572	0644	edit dl rm
perlinterp.pod	33687	0644	edit dl rm
perlintro.pod	22119	0644	edit dl rm
perliol.pod	34185	0644	edit dl rm
perlipc.pod	70829	0644	edit dl rm
perlirix.pod	4395	0644	edit dl rm
perljp.pod	7521	0644	edit dl rm
perlko.pod	12259	0644	edit dl rm
perllexwarn.pod	355	0644	edit dl rm
perllinux.pod	1488	0644	edit dl rm
perllocale.pod	68678	0644	edit dl rm
perllol.pod	9580	0644	edit dl rm
perlmacos.pod	1001	0644	edit dl rm
perlmacosx.pod	12060	0644	edit dl rm
perlmod.pod	26250	0644	edit dl rm
perlmodinstall.pod	12792	0644	edit dl rm
perlmodlib.pod	76482	0644	edit dl rm
perlmodstyle.pod	22575	0644	edit dl rm
perlmroapi.pod	3212	0644	edit dl rm
perlnetware.pod	6648	0644	edit dl rm
perlnewmod.pod	11036	0644	edit dl rm
perlnumber.pod	8353	0644	edit dl rm
perlobj.pod	35537	0644	edit dl rm
perlootut.pod	26783	0644	edit dl rm
perlop.pod	136252	0644	edit dl rm
perlopenbsd.pod	1204	0644	edit dl rm
perlopentut.pod	9455	0644	edit dl rm
perlos2.pod	93351	0644	edit dl rm
perlos390.pod	15674	0644	edit dl rm
perlos400.pod	4768	0644	edit dl rm
perlpacktut.pod	51282	0644	edit dl rm
perlperf.pod	49881	0644	edit dl rm
perlplan9.pod	5125	0644	edit dl rm
perlpod.pod	22196	0644	edit dl rm
perlpodspec.pod	68476	0644	edit dl rm
perlpolicy.pod	25629	0644	edit dl rm
perlport.pod	87602	0644	edit dl rm
perlpragma.pod	5176	0644	edit dl rm
perlqnx.pod	6673	0644	edit dl rm
perlre.pod	120901	0644	edit dl rm
perlreapi.pod	30334	0644	edit dl rm
perlrebackslash.pod	31817	0644	edit dl rm
perlrecharclass.pod	49029	0644	edit dl rm
perlref.pod	35304	0644	edit dl rm
perlreftut.pod	18790	0644	edit dl rm
perlreguts.pod	38328	0644	edit dl rm
perlrepository.pod	509	0644	edit dl rm
perlrequick.pod	18497	0644	edit dl rm
perlreref.pod	14744	0644	edit dl rm
perlretut.pod	121257	0644	edit dl rm
perlriscos.pod	1529	0644	edit dl rm
perlrun.pod	53550	0644	edit dl rm
perlsec.pod	26184	0644	edit dl rm
perlsolaris.pod	29822	0644	edit dl rm
perlsource.pod	6876	0644	edit dl rm
perlstyle.pod	8630	0644	edit dl rm
perlsub.pod	72967	0644	edit dl rm
perlsymbian.pod	15359	0644	edit dl rm
perlsyn.pod	44512	0644	edit dl rm
perlsynology.pod	7778	0644	edit dl rm
perlthrtut.pod	46459	0644	edit dl rm
perltie.pod	38607	0644	edit dl rm
perltoc.pod	694171	0644	edit dl rm
perltodo.pod	376	0644	edit dl rm
perltooc.pod	294	0644	edit dl rm
perltoot.pod	294	0644	edit dl rm
perltrap.pod	10620	0644	edit dl rm
perltru64.pod	8492	0644	edit dl rm
perltw.pod	4477	0644	edit dl rm
perlunicode.pod	82491	0644	edit dl rm
perlunicook.pod	25488	0644	edit dl rm
perlunifaq.pod	13647	0644	edit dl rm
perluniintro.pod	38340	0644	edit dl rm
perluniprops.pod	285306	0644	edit dl rm
perlunitut.pod	7951	0644	edit dl rm
perlutil.pod	7640	0644	edit dl rm
perlvar.pod	78364	0644	edit dl rm
perlvms.pod	50823	0644	edit dl rm
perlvos.pod	3843	0644	edit dl rm
perlwin32.pod	39298	0644	edit dl rm
perlxs.pod	78920	0644	edit dl rm
perlxstut.pod	50095	0644	edit dl rm
perlxstypemap.pod	24001	0644	edit dl rm

Edit: /usr/share/perl5/pod/perlpragma.pod (5176B)

=head1 NAME

perlpragma - how to write a user pragma

=head1 DESCRIPTION

A pragma is a module which influences some aspect of the compile time or run
time behaviour of Perl, such as C<strict> or C<warnings>. With Perl 5.10 you
are no longer limited to the built in pragmata; you can now create user
pragmata that modify the behaviour of user functions within a lexical scope.

=head1 A basic example

For example, say you need to create a class implementing overloaded
mathematical operators, and would like to provide your own pragma that
functions much like C<use integer;> You'd like this code

use MyMaths;

my $l = MyMaths->new(1.2);
    my $r = MyMaths->new(3.4);

print "A: ", $l + $r, "\n";

use myint;
    print "B: ", $l + $r, "\n";

{
        no myint;
        print "C: ", $l + $r, "\n";
    }

print "D: ", $l + $r, "\n";

no myint;
    print "E: ", $l + $r, "\n";

to give the output

A: 4.6
    B: 4
    C: 4.6
    D: 4
    E: 4.6

I<i.e.>, where C<use myint;> is in effect, addition operations are forced
to integer, whereas by default they are not, with the default behaviour being
restored via C<no myint;>

The minimal implementation of the package C<MyMaths> would be something like
this:

package MyMaths;
    use warnings;
    use strict;
    use myint();
    use overload '+' => sub {
        my ($l, $r) = @_;
	# Pass 1 to check up one call level from here
        if (myint::in_effect(1)) {
            int($$l) + int($$r);
        } else {
            $$l + $$r;
        }
    };

sub new {
        my ($class, $value) = @_;
        bless \$value, $class;
    }

Note how we load the user pragma C<myint> with an empty list C<()> to
prevent its C<import> being called.

The interaction with the Perl compilation happens inside package C<myint>:

package myint;

use strict;
    use warnings;

sub import {
        $^H{"myint/in_effect"} = 1;
    }

sub unimport {
        $^H{"myint/in_effect"} = 0;
    }

sub in_effect {
        my $level = shift // 0;
        my $hinthash = (caller($level))[10];
        return $hinthash->{"myint/in_effect"};
    }

As pragmata are implemented as modules, like any other module, C<use myint;>
becomes

BEGIN {
        require myint;
        myint->import();
    }

and C<no myint;> is

BEGIN {
        require myint;
        myint->unimport();
    }

Hence the C<import> and C<unimport> routines are called at B<compile time>
for the user's code.

User pragmata store their state by writing to the magical hash C<%^H>,
hence these two routines manipulate it. The state information in C<%^H> is
stored in the optree, and can be retrieved read-only at runtime with C<caller()>,
at index 10 of the list of returned results. In the example pragma, retrieval
is encapsulated into the routine C<in_effect()>, which takes as parameter
the number of call frames to go up to find the value of the pragma in the
user's script. This uses C<caller()> to determine the value of
C<$^H{"myint/in_effect"}> when each line of the user's script was called, and
therefore provide the correct semantics in the subroutine implementing the
overloaded addition.

=head1 Key naming

There is only a single C<%^H>, but arbitrarily many modules that want
to use its scoping semantics.  To avoid stepping on each other's toes,
they need to be sure to use different keys in the hash.  It is therefore
conventional for a module to use only keys that begin with the module's
name (the name of its main package) and a "/" character.  After this
module-identifying prefix, the rest of the key is entirely up to the
module: it may include any characters whatsoever.  For example, a module
C<Foo::Bar> should use keys such as C<Foo::Bar/baz> and C<Foo::Bar/$%/_!>.
Modules following this convention all play nicely with each other.

The Perl core uses a handful of keys in C<%^H> which do not follow this
convention, because they predate it.  Keys that follow the convention
won't conflict with the core's historical keys.

=head1 Implementation details

The optree is shared between threads.  This means there is a possibility that
the optree will outlive the particular thread (and therefore the interpreter
instance) that created it, so true Perl scalars cannot be stored in the
optree.  Instead a compact form is used, which can only store values that are
integers (signed and unsigned), strings or C<undef> - references and
floating point values are stringified.  If you need to store multiple values
or complex structures, you should serialise them, for example with C<pack>.
The deletion of a hash key from C<%^H> is recorded, and as ever can be
distinguished from the existence of a key with value C<undef> with
C<exists>.

B<Don't> attempt to store references to data structures as integers which
are retrieved via C<caller> and converted back, as this will not be threadsafe.
Accesses would be to the structure without locking (which is not safe for
Perl's scalars), and either the structure has to leak, or it has to be
freed when its creating thread terminates, which may be before the optree
referencing it is deleted, if other threads outlive it.

=head1 NAME perlpragma - how to write a user pragma =head1 DESCRIPTION A pragma is a module which influences some aspect of the compile time or run time behaviour of Perl, such as C or C. With Perl 5.10 you are no longer limited to the built in pragmata; you can now create user pragmata that modify the behaviour of user functions within a lexical scope. =head1 A basic example For example, say you need to create a class implementing overloaded mathematical operators, and would like to provide your own pragma that functions much like C You'd like this code use MyMaths; my $l = MyMaths->new(1.2); my $r = MyMaths->new(3.4); print "A: ", $l + $r, "\n"; use myint; print "B: ", $l + $r, "\n"; { no myint; print "C: ", $l + $r, "\n"; } print "D: ", $l + $r, "\n"; no myint; print "E: ", $l + $r, "\n"; to give the output A: 4.6 B: 4 C: 4.6 D: 4 E: 4.6 I, where C is in effect, addition operations are forced to integer, whereas by default they are not, with the default behaviour being restored via C The minimal implementation of the package C would be something like this: package MyMaths; use warnings; use strict; use myint(); use overload '+' => sub { my ($l, $r) = @_; # Pass 1 to check up one call level from here if (myint::in_effect(1)) { int($$l) + int($$r); } else { $$l + $$r; } }; sub new { my ($class, $value) = @_; bless \$value, $class; } 1; Note how we load the user pragma C with an empty list C<()> to prevent its C being called. The interaction with the Perl compilation happens inside package C: package myint; use strict; use warnings; sub import { $^H{"myint/in_effect"} = 1; } sub unimport { $^H{"myint/in_effect"} = 0; } sub in_effect { my $level = shift // 0; my $hinthash = (caller($level))[10]; return $hinthash->{"myint/in_effect"}; } 1; As pragmata are implemented as modules, like any other module, C becomes BEGIN { require myint; myint->import(); } and C is BEGIN { require myint; myint->unimport(); } Hence the C and C routines are called at B for the user's code. User pragmata store their state by writing to the magical hash C<%^H>, hence these two routines manipulate it. The state information in C<%^H> is stored in the optree, and can be retrieved read-only at runtime with C, at index 10 of the list of returned results. In the example pragma, retrieval is encapsulated into the routine C, which takes as parameter the number of call frames to go up to find the value of the pragma in the user's script. This uses C to determine the value of C<$^H{"myint/in_effect"}> when each line of the user's script was called, and therefore provide the correct semantics in the subroutine implementing the overloaded addition. =head1 Key naming There is only a single C<%^H>, but arbitrarily many modules that want to use its scoping semantics. To avoid stepping on each other's toes, they need to be sure to use different keys in the hash. It is therefore conventional for a module to use only keys that begin with the module's name (the name of its main package) and a "/" character. After this module-identifying prefix, the rest of the key is entirely up to the module: it may include any characters whatsoever. For example, a module C should use keys such as C and C. Modules following this convention all play nicely with each other. The Perl core uses a handful of keys in C<%^H> which do not follow this convention, because they predate it. Keys that follow the convention won't conflict with the core's historical keys. =head1 Implementation details The optree is shared between threads. This means there is a possibility that the optree will outlive the particular thread (and therefore the interpreter instance) that created it, so true Perl scalars cannot be stored in the optree. Instead a compact form is used, which can only store values that are integers (signed and unsigned), strings or C - references and floating point values are stringified. If you need to store multiple values or complex structures, you should serialise them, for example with C. The deletion of a hash key from C<%^H> is recorded, and as ever can be distinguished from the existence of a key with value C with C. B attempt to store references to data structures as integers which are retrieved via C and converted back, as this will not be threadsafe. Accesses would be to the structure without locking (which is not safe for Perl's scalars), and either the structure has to leak, or it has to be freed when its creating thread terminates, which may be before the optree referencing it is deleted, if other threads outlive it.