Perl

Much like Octave, Perl has its own language-specific build system.

Phases

The PerlBuilder and PerlPackage base classes come with 3 phases that can be overridden:

configure - configure the package
build - build the package
install - install the package

Perl packages have 2 common modules used for module installation:

`ExtUtils::MakeMaker`

The ExtUtils::MakeMaker module is just what it sounds like, a module designed to generate Makefiles. It can be identified by the presence of a Makefile.PL file, and has the following installation steps:

$ perl Makefile.PL INSTALL_BASE=/path/to/installation/prefix
$ make
$ make test  # optional
$ make install

`Module::Build`

The Module::Build module is a pure-Perl build system, and can be identified by the presence of a Build.PL file. It has the following installation steps:

$ perl Build.PL --install_base /path/to/installation/prefix
$ ./Build
$ ./Build test  # optional
$ ./Build install

If both Makefile.PL and Build.PL files exist in the package, Spack will use Makefile.PL by default. If your package uses a different module, PerlPackage will need to be extended to support it.

PerlPackage automatically detects which build steps to use, so there shouldn’t be much work on the package developer’s side to get things working.

Finding Perl packages

Most Perl modules are hosted on CPAN - The Comprehensive Perl Archive Network. If you need to find a package for XML::Parser, for example, you should search for “CPAN XML::Parser”.

Some CPAN pages are versioned. Check for a link to the “Latest Release” to make sure you have the latest version.

Package name

When you use spack create to create a new Perl package, Spack will automatically prepend perl- to the front of the package name. This helps to keep Perl modules separate from other packages. The same naming scheme is used for other language extensions, like Python and R.

Description

Most CPAN pages have a short description under “NAME” and a longer description under “DESCRIPTION”. Use whichever you think is more useful while still being succinct.

Homepage

In the top-right corner of the CPAN page, you’ll find a “permalink” for the package. This should be used instead of the current URL, as it doesn’t contain the version number and will always link to the latest release.

URL

If you haven’t found it already, the download URL is on the right side of the page below the permalink. Search for “Download”.

Build system dependencies

Every PerlPackage obviously depends on Perl at build and run-time, so PerlPackage contains:

extends('perl')

If your package requires a specific version of Perl, you should specify this.

Although newer versions of Perl include ExtUtils::MakeMaker and Module::Build as “core” modules, you may want to add dependencies on perl-extutils-makemaker and perl-module-build anyway. Many people add Perl as an external package, and we want the build to work properly. If your package uses Makefile.PL to build, add:

depends_on('perl-extutils-makemaker', type='build')

If your package uses Build.PL to build, add:

depends_on('perl-module-build', type='build')

Perl dependencies

Below the download URL, you will find a “Dependencies” link, which takes you to a page listing all of the dependencies of the package. Packages listed as “Core module” don’t need to be added as dependencies, but all direct dependencies should be added. Don’t add dependencies of dependencies. These should be added as dependencies to the dependency, not to your package.

Passing arguments to configure

Packages that have non-Perl dependencies often use command-line variables to specify their installation directory. You can pass arguments to Makefile.PL or Build.PL by overriding configure_args like so:

def configure_args(self):
    expat = self.spec['expat'].prefix

    return [
        'EXPATLIBPATH={0}'.format(expat.lib),
        'EXPATINCPATH={0}'.format(expat.include),
    ]

Alternatives to Spack

If you need to maintain a stack of Perl modules for a user and don’t want to add all of them to Spack, a good alternative is cpanm. If Perl is already installed on your system, it should come with a cpan executable. To install cpanm, run the following command:

$ cpan App::cpanminus

Now, you can install any Perl module you want by running:

$ cpanm Module::Name

Obviously, these commands can only be run if you have root privileges. Furthermore, cpanm is not capable of installing non-Perl dependencies. If you need to install to your home directory or need to install a module with non-Perl dependencies, Spack is a better option.

External documentation

You can find more information on installing Perl modules from source at: http://www.perlmonks.org/?node_id=128077

More generic Perl module installation instructions can be found at: http://www.cpan.org/modules/INSTALL.html