This document describes the layout of the Perl source tree. If you're
       hacking on the Perl core, this will help you find what you're looking

       The Perl source tree is big. Here's some of the thing you'll find in

   C code
       The C source code and header files mostly live in the root of the
       source tree. There are a few platform-specific directories which
       contain C code. In addition, some of the modules shipped with Perl
       include C or XS code.

       See perlinterp for more details on the files that make up the Perl
       interpreter, as well as details on how it works.

   Core modules
       Modules shipped as part of the Perl core live in four subdirectories.
       Two of these directories contain modules that live in the core, and two
       contain modules that can also be released separately on CPAN. Modules
       which can be released on cpan are known as "dual-life" modules.

       o   lib/

           This directory contains pure-Perl modules which are only released
           as part of the core. This directory contains all of the modules and
           their tests, unlike other core modules.

       o   ext/

           This directory contains XS-using modules which are only released as
           part of the core. These modules generally have their Makefile.PL
           and are laid out more like a typical CPAN module.

       o   dist/

           This directory is for dual-life modules where the blead source is
           canonical. Note that some modules in this directory may not yet
           have been released separately on CPAN.

       o   cpan/

           This directory contains dual-life modules where the CPAN module is
           canonical. Do not patch these modules directly! Changes to these
           modules should be submitted to the maintainer of the CPAN module.
           Once those changes are applied and released, the new version of the
           module will be incorporated into the core.

       For some dual-life modules, it has not yet been determined if the CPAN
       version or the blead source is canonical. Until that is done, those
       modules should be in cpan/.
           subdirectories for each module, like a standard CPAN distribution.

       o   t/base/

           Tests for the absolute basic functionality of Perl. This includes
           "if", basic file reads and writes, simple regexes, etc. These are
           run first in the test suite and if any of them fail, something is
           really broken.

       o   t/cmd/

           Tests for basic control structures, "if/else", "while",
           subroutines, etc.

       o   t/comp/

           Tests for basic issues of how Perl parses and compiles itself.

       o   t/io/

           Tests for built-in IO functions, including command line arguments.

       o   t/mro/

           Tests for perl's method resolution order implementations (see mro).

       o   t/op/

           Tests for perl's built in functions that don't fit into any of the
           other directories.

       o   t/re/

           Tests for regex related functions or behaviour. (These used to live
           in t/op).

       o   t/run/

           Tests for features of how perl actually runs, including exit codes
           and handling of PERL* environment variables.

       o   t/uni/

           Tests for the core support of Unicode.

       o   t/win32/

           Windows-specific tests.

       o   t/porting/

           Tests the state of the source tree for various common errors. For
           example, it tests that everyone who is listed in the git log has a
           corresponding entry in the AUTHORS file.

       All of the core documentation intended for end users lives in pod/.
       Individual modules in lib/, ext/, dist/, and cpan/ usually have their
       own documentation, either in the file or an accompanying
       Module.pod file.

       Finally, documentation intended for core Perl developers lives in the
       Porting/ directory.

   Hacking toolks and documentation
       The Porting directory contains a grab bag of code and documentation
       intended to help porters work on Perl. Some of the highlights include:

       o   check*

           These are scripts which will check the source things like ANSI C
           violations, POD encoding issues, etc.

       o   Maintainers,, and

           These files contain information on who maintains which modules. Run
           "perl Porting/Maintainers -M Module::Name" to find out more
           information about a dual-life module.

       o   podtidy

           Tidies a pod file. It's a good idea to run this on a pod file
           you've patched.

   Build system
       The Perl build system starts with the Configure script in the root

       Platform-specific pieces of the build system also live in platform-
       specific directories like win32/, vms/, etc.

       The Configure script is ultimately responsible for generating a

       The build system that Perl uses is called metaconfig. This system is
       maintained separately from the Perl core.

       The metaconfig system has its own git repository. Please see its README
       file in <> for more details.

       The Cross directory contains various files related to cross-compiling
       Perl. See Cross/README for more details.

       This file everyone who's contributed to Perl. If you submit a patch,
       you should add your name to this file as part of the patch.

       The MANIFEST file in the root of the source tree contains a list of
       every file in the Perl core, as well as a brief description of each
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