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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 for.


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.

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.


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:

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 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 file.

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

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