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.IX Title "cpanfile-faq 3"
.TH cpanfile-faq 3 2026-07-15 "perl v5.42.2" "User Contributed Perl Documentation"
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.SH NAME
cpanfile\-faq \- cpanfile FAQ
.SH QUESTIONS
.IX Header "QUESTIONS"
.SS "Does cpanfile replace Makefile.PL/Build.PL or META.yml/json?"
.IX Subsection "Does cpanfile replace Makefile.PL/Build.PL or META.yml/json?"
No, it doesn\*(Aqt. \f(CW\*(C`cpanfile\*(C'\fR is a simpler way to declare CPAN
dependencies, mainly for \fIyour application\fR rather than CPAN
distributions.
.PP
However, while CPAN distributions do not need to \fBswitch\fR to
\&\f(CW\*(C`cpanfile\*(C'\fR, you can certainly \fImanage\fR the dependencies in
\&\f(CW\*(C`cpanfile\*(C'\fR, then export them into \f(CW\*(C`META.json\*(C'\fR files when shipping to
CPAN, using tools such as Dist::Milla or Module::Install::CPANfile
.SS "Why do we need yet another format?"
.IX Subsection "Why do we need yet another format?"
Here are some of the reasons that motivates the new cpanfile
format.
.IP "Not everything is a CPAN distribution" 4
.IX Item "Not everything is a CPAN distribution"
First of all, it is annoying to write (a dummy) \f(CW\*(C`Makefile.PL\*(C'\fR when
what you develop is not a CPAN distribution, just so that installation
like \f(CW\*(C`cpanm \-\-installdeps .\*(C'\fR would work.
.Sp
It gets more painful when you develop a web application that you want
to deploy on a different environment using version control system
(such as PaaS/cloud infrastructure), because it requires you to often
commit the META file or \f(CW\*(C`inc/\*(C'\fR directory (or even worse, both) to a
repository.
.Sp
Many web application frameworks generate a boiler\-plate \f(CW\*(C`Makefile.PL\*(C'\fR
for dependency declaration and to let you install dependencies with
\&\f(CW\*(C`cpanm \-\-installdeps .\*(C'\fR, but that doesn\*(Aqt always mean they are
meant to be installed. Things can be often much simpler if you run the
application from the checkout directory.
.Sp
With cpanfile, dependencies can be installed either globally or
locally using supported tools such as cpanm or Carton. Because
\&\f(CW\*(C`cpanfile\*(C'\fR lists all the dependencies of your entire application and
will be updated over time, it makes perfect sense to commit the file
to a version control system, and push the file for a deployment.
.IP "Familiar DSL syntax" 4
.IX Item "Familiar DSL syntax"
This is a new file type, but the format and syntax isn\*(Aqt entirely
new. The metadata it can declare is exactly a subset of "Prereqs" in
CPAN Meta Spec.
.Sp
The syntax borrows a lot from Module::Install. Module::Install is a
great way to easily declare module metadata such as name, author and
dependencies. cpanfile format is simply to extract the dependencies
into a separate file, which means most of the developers are familiar
with the syntax.
.IP "Complete CPAN Meta Spec v2 support" 4
.IX Item "Complete CPAN Meta Spec v2 support"
\&\f(CW\*(C`cpanfile\*(C'\fR basically allows you to declare CPAN::Meta::Spec
prerequisite specification using an easy Perl DSL syntax. This makes
it easy to declare per\-phase dependencies and newer version 2 features
such as conflicts and version ranges.
.ie n .SS "How can I start using ""cpanfile""?"
.el .SS "How can I start using \f(CWcpanfile\fP?"
.IX Subsection "How can I start using cpanfile?"
First of all, most distributions on CPAN are not required to update to
this format.
.PP
If your application currently uses \f(CW\*(C`Makefile.PL\*(C'\fR etc. for dependency
declaration because of the current toolchain implementation (e.g. \f(CW\*(C`cpanm \-\-installdeps .\*(C'\fR), you can upgrade to \f(CW\*(C`cpanfile\*(C'\fR while
keeping the build file based installation working for the backward
compatibility.
.PP
If you are an author of CPAN module and want to manage CPAN module
prerequisites using \f(CW\*(C`cpanfile\*(C'\fR you can use one of the following
tools:
.IP Dist::Milla 4
.IX Item "Dist::Milla"
Dist::Milla is a profile for Dist::Zilla that has a \f(CW\*(C`cpanfile\*(C'\fR
support to declare dependencies for your module.
.IP Dist::Zilla 4
.IX Item "Dist::Zilla"
Dist::Zilla::Plugin::Prereqs::FromCPANfile provides a way to merge
dependencies declared in \f(CW\*(C`cpanfile\*(C'\fR into META files as well as build
files. You can combine them using other prerequisite scanners like
\&\f(CW\*(C`AutoPrereqs\*(C'\fR.
.IP Minilla 4
.IX Item "Minilla"
Minilla is a yet another authoring tool that supports \f(CW\*(C`cpanfile\*(C'\fR
as a way to describe dependencies for your CPAN module.
.IP Module::Install 4
.IX Item "Module::Install"
Module::Install::CPANfile provides a \f(CW\*(C`cpanfile\*(C'\fR DSL that reads
\&\f(CW\*(C`cpanfile\*(C'\fR to merge prerequisites when dumping \f(CW\*(C`MYMETA\*(C'\fR files upon
installation.
.IP Module::Build 4
.IX Item "Module::Build"
Module::Build::Pluggable::CPANfile merges \f(CW\*(C`cpanfile\*(C'\fR dependencies
from \f(CW\*(C`Build.PL\*(C'\fR when dumping out MYMETA information.
.Sp
However you\*(Aqre recommended to switch to an authoring system that emits
\&\f(CW\*(C`Build.PL\*(C'\fR with parsed CPANfile information, like Dist::Zilla
mentioned above.
.IP ExtUtils::MakeMaker 4
.IX Item "ExtUtils::MakeMaker"
ExtUtils::MakeMaker::CPANfile merges \f(CW\*(C`cpanfile\*(C'\fR prerequisites
when dumping \f(CW\*(C`MYMETA\*(C'\fR files upon installation.
.Sp
However you\*(Aqre recommended to switch to an authoring system that emits
\&\f(CW\*(C`Makefile.PL\*(C'\fR with parsed CPANfile information, like Dist::Zilla
mentioned above.