man > perlsource(1)

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

NAME
       perlsource - A guide to the Perl source tree

DESCRIPTION
       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 for.

FINDING YOUR WAY AROUND
       The Perl source tree is big. Here's some of the thing you'll find in it:

   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.

       •   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.

       •   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 blead.

       •   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.

       •   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/.

   Tests
       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.

       •   Module tests

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

       •   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.

       •   t/cmd/

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

       •   t/comp/

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

       •   t/io/

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

       •   t/mro/

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

       •   t/op/

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

       •   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/test.pl,as  that  program
           depends on functionality which the test file itself is testing.

       •   t/re/

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

       •   t/run/

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

       •   t/uni/

           Tests for the core support of Unicode.

       •   t/win32/

           Windows-specific tests.

       •   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.

       •   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!

   Documentation
       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  Module.pm
       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:

       •   check*

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

       •   Maintainers, Maintainers.pl, and Maintainers.pm

           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.

       •   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 on *nix-like systems starts with  the  Configure  script  in  the  root
       directory.

       Platform-specific  pieces of the build system also live in platform-specific directories like
       win32/, vms/, etc.   Windows  and  VMS  have  their  own  Configure-like  scripts,  in  their
       respective directories.

       The  Configure  script  (or a platform-specific similar script) is ultimately responsible for
       generating a Makefile from Makefile.SH.

       The build system that Perl uses is called metaconfig. This system  is  maintained  separately
       from  the Perl core, and knows about the platform-specific Configure-like scripts, as well as
       Configure itself.

       The  metaconfig  system  has  its  own  git  repository.  Please  see  its  README  file   in
       <https://github.com/Perl/metaconfig> for more details.

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

   AUTHORS
       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.

   MANIFEST
       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 file.

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

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

perl v5.38.2                                 2026-06-12                                PERLSOURCE(1)