Module::XSOrPP - Determine if an installed module is XS or pure-perl


This document describes version 0.120 of Module::XSOrPP (from Perl distribution Module-XSOrPP), released on 2023-07-09.


 use Module::XSOrPP qw(
     is_xs is_pp xs_or_pp

 say "Class::XSAccessor is an XS module" if is_xs("Class/");
 say "JSON::PP is a pure-Perl module" if is_pp("JSON::PP");
 say "Params::Util is an XS module with PP fallback" if xs_or_pp("Class/") =~ /^(xs|xs_or_pp)$/;



xs_or_pp($mod, \%opts) => str

Return either "xs", "pp", or "xs_or_pp" (XS with a PP fallback). Return undef if can't determine which. $mod value can be in the form of Package/ or Package::SubPkg. The following ways are tried, in order:

  • Predetermined list

    Some CPAN modules are XS with a PP fallback. This module maintains the list.

  • Looking at the .packlist

    If a .{bs,so,dll} file is listed in the .packlist, then it is assumed to be an XS module. This method will fail if there is no .packlist available (e.g. core or uninstalled or when the package management strips the packlist), or if a dist contains both pure-Perl and XS.

  • Looking at the source file for usage of XSLoader or DynaLoader

    If the module source code has something like use XSLoader; or <use DynaLoader;> then it is assumed to be an XS module. This is currently implemented using a simple regex, so it is somewhat brittle.

  • Guessing from the name

    If the module has "XS" in its name then it's assumed to be an XS module. If the module has "PP" in its name, it's assumed to be a pure-Perl module.

    Known false positives will be prevented in the future.

Other methods will be added in the future (e.g. a database like in Module::CoreList, consulting MetaCPAN, etc).


  • warn => BOOL (default: 0)

    If set to true, will warn to STDERR if fail to determine.

  • debug => BOOL (default: 0)

    If set to true will print debugging message to STDERR.

is_xs($mod, \%opts) => BOOL

Return true if module $mod is an XS module, false if a pure Perl module, or undef if can't determine either. See xs_or_pp for more details.

is_pp($mod, \%opts) => BOOL

Return true if module $mod is a pure Perl module or XS module with a PP fallback. See is_xs for more details. See xs_or_pp for more details.


Please visit the project's homepage at


Source repository is at


perlancar <>


Steven Haryanto <>


To contribute, you can send patches by email/via RT, or send pull requests on GitHub.

Most of the time, you don't need to build the distribution yourself. You can simply modify the code, then test via:

 % prove -l

If you want to build the distribution (e.g. to try to install it locally on your system), you can install Dist::Zilla, Dist::Zilla::PluginBundle::Author::PERLANCAR, Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps required beyond that are considered a bug and can be reported to me.


This software is copyright (c) 2023, 2016, 2015, 2014 by perlancar <>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.