Modules
A module is a package defined in a
file with a name that is the same as the package’s. Perl locates
modules by searching the @INC
array, which contains a list of library directories. Perl’s use of
@INC is roughly comparable to the
Unix shell’s use of the PATH environment variable to locate executable
programs. @INC is defined when Perl
is built and can be supplemented with the -I
command-line option to Perl or with use
lib within a program.
When you refer to ModuleName
in your program, Perl searches in the directories listed in @INC for the module file
ModuleName.pm and uses the first one it finds.
When you refer to a module embedded in another package, such as
ParentPackage::ModuleName, Perl
looks for a ParentPackage/ subdirectory in the
@INC path, and for a
ModuleName.pm file in that subdirectory.
Every Perl installation includes a central lib directory. The actual pathname of this directory varies from system to system, but it’s commonly /usr/lib/perl or /usr/local/lib/perl. Looking at the central lib directory for your Perl distribution, you’ll see something like this:
% ls -aF /usr/local/lib/perl ./ I18N/ bigfloat.pl less.pm ../ IO/ bigint.pl lib.pm AnyDBM_File.pm IPC/ bigrat.pl locale.pm AutoLoader.pm Math/ blib.pm look.pl AutoSplit.pm Net/ cacheout.pl man/ Benchmark.pm Pod/ chat2.pl newgetopt.pl Bundle/ Search/ complete.pl open2.pl CGI/ SelectSaver.pm constant.pm open3.pl CGI.pm SelfLoader.pm ctime.pl perl5db.pl CPAN/ Shell.pm diagnostics.pm pod/ CPAN.pm Symbol.pm dotsh.pl ...
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