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Diffstat (limited to 'pod/perlmod.pod')
| -rw-r--r-- | pod/perlmod.pod | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/pod/perlmod.pod b/pod/perlmod.pod index 99d08eb4f8..fc49e34d67 100644 --- a/pod/perlmod.pod +++ b/pod/perlmod.pod @@ -5,6 +5,7 @@ perlmod - Perl modules (packages and symbol tables) =head1 DESCRIPTION =head2 Packages +X<package> X<namespace> X<variable, global> X<global variable> X<global> Perl provides a mechanism for alternative namespaces to protect packages from stomping on each other's variables. In fact, there's @@ -38,6 +39,7 @@ supported for backwards compatibility, if you try to use a string like C<"This is $owner's house">, you'll be accessing C<$owner::s>; that is, the $s variable in package C<owner>, which is probably not what you meant. Use braces to disambiguate, as in C<"This is ${owner}'s house">. +X<::> X<'> Packages may themselves contain package separators, as in C<$OUTER::INNER::var>. This implies nothing about the order of @@ -57,6 +59,7 @@ even when used for other purposes than their built-in ones. If you have a package called C<m>, C<s>, or C<y>, then you can't use the qualified form of an identifier because it would be instead interpreted as a pattern match, a substitution, or a transliteration. +X<variable, punctuation> Variables beginning with underscore used to be forced into package main, but we decided it was more useful for package writers to be able @@ -83,6 +86,7 @@ See L<perlsub> for other scoping issues related to my() and local(), and L<perlref> regarding closures. =head2 Symbol Tables +X<symbol table> X<stash> X<%::> X<%main::> X<typeglob> X<glob> X<alias> The symbol table for a package happens to be stored in the hash of that name with two colons appended. The main symbol table's name is thus @@ -179,6 +183,7 @@ when you don't want to have to remember to dereference variables explicitly. Another use of symbol tables is for making "constant" scalars. +X<constant> X<scalar, constant> *PI = \3.14159265358979; @@ -254,6 +259,7 @@ This also has implications for the use of the SUPER:: qualifier (see L<perlobj>). =head2 BEGIN, CHECK, INIT and END +X<BEGIN> X<CHECK> X<INIT> X<END> Four specially named code blocks are executed at the beginning and at the end of a running Perl program. These are the C<BEGIN>, C<CHECK>, C<INIT>, and @@ -299,6 +305,7 @@ Inside an C<END> code block, C<$?> contains the value that the program is going to pass to C<exit()>. You can modify C<$?> to change the exit value of the program. Beware of changing C<$?> by accident (e.g. by running something via C<system>). +X<$?> C<CHECK> and C<INIT> code blocks are useful to catch the transition between the compilation phase and the execution phase of the main program. @@ -348,6 +355,7 @@ The B<begincheck> program makes it all clear, eventually: __END__ =head2 Perl Classes +X<class> X<@ISA> There is no special class syntax in Perl, but a package may act as a class if it provides subroutines to act as methods. Such a @@ -358,6 +366,7 @@ must be a package global, not a lexical). For more on this, see L<perltoot> and L<perlobj>. =head2 Perl Modules +X<module> A module is just a set of related functions in a library file, i.e., a Perl package with the same name as the file. It is specifically @@ -529,6 +538,9 @@ although the POSIX module happens to do both dynamic loading and autoloading, the user can say just C<use POSIX> to get it all. =head2 Making your module threadsafe +X<threadsafe> X<thread safe> +X<module, threadsafe> X<module, thread safe> +X<CLONE> X<CLONE_SKIP> X<thread> X<threads> X<ithread> Since 5.6.0, Perl has had support for a new type of threads called interpreter threads (ithreads). These threads can be used explicitly |