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PERLSOURCE(1)	       Perl Programmers	Reference Guide		 PERLSOURCE(1)

       perlsource - A guide to the Perl	source tree

       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/

	   Like	lib/, this directory contains modules which are	only released
	   as part of the core.	 Unlike	lib/, however, a module	under ext/
	   generally has a CPAN-style directory- and file-layout and its own
	   Makefile.PL.	 There is no expectation that a	module under ext/ will
	   work	with earlier versions of Perl 5.  Hence, such a	module may
	   take	full advantage of syntactical and other	improvements in	Perl 5

       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.  Modules under dist/ should
	   make	an effort to work with earlier versions	of Perl	5.

       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/.

       The Perl	core has an extensive test suite. If you add new tests (or new
       modules with tests), you	may need to update the t/TEST file so that the
       tests are run.

       o   Module tests

	   Tests for core modules in the lib/ directory	are right next to the
	   module itself. For example, we have lib/ and lib/strict.t.

	   Tests for modules in	ext/ and the dual-life modules are in t/
	   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/opbasic/

	   Tests for perl's built in functions which, like those in t/op/, do
	   not fit into	any of the other directories, but which, in addition,
	   cannot use t/,as that	program	depends	on functionality which
	   the test file itself	is testing.

       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.

       o   t/lib/

	   The old home	for the	module tests, you shouldn't put	anything new
	   in here. There are still some bits and pieces hanging around	in
	   here	that need to be	moved. Perhaps you could move them?  Thanks!

       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 tools 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 lists 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

       You can get an overview of all the files	with this command:

	 % perl	-lne 'print if /^[^\/]+\.[ch]\s+/' MANIFEST

perl v5.28.3			  2020-05-14			 PERLSOURCE(1)


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