Perl package management#

Introduction#

(Note: the Perl community uses the term ‘modules’ rather than ‘packages’, however, in the documentation, we use the term ‘packages’ to try and avoid confusion with the module system for loading software.)

Perl comes with an extensive standard library, and you are strongly encouraged to use those packages as much as possible, since this will ensure that your code can be run on any platform that supports Perl.

However, many useful extensions to and libraries for Perl come in the form of packages that can be installed separately. Some of those are part of the Perl modules available on VSC infrastructure.

Given the astounding number of packages, it is not sustainable to install each and everyone system wide. This section explains shows how users can install Perl packages themselves.

Checking for installed Perl packages#

To check which Perl packages are installed, the cpan utility is useful. It will list all packages that are installed for the Perl distribution you are using, including those installed by you, i.e., those in your PERL5LIB environment variable.

Load the module for the Perl version you wish to use, e.g.,
```
$ module load Perl/5.40.0-GCCcore-14.2.0
```
In general it is recommended to also load the corresponding Perl-bundle-CPAN module, which makes a lot of Perl packages available (note it is also sufficient to only load this module, since the correct Perl module will be loaded automatically as a dependency)
```
$ module load Perl-bundle-CPAN/5.40.0-GCCcore-14.2.0
```
Run cpan (this will provide a lot of output):
```
$ cpan  -l
```

Installing your own Perl packages#

Setting up your own package repository for Perl is straightforward. For this purpose, the cpan utility first needs to be configured.

Load the appropriate Perl module(s), e.g.,

$ module load Perl-bundle-CPAN/5.40.0-GCCcore-14.2.0

Create a directory to install in, i.e.,
```
$ mkdir ${VSC_DATA}/perl5
```
Run cpan:
```
$ cpan
```
The first time you run cpan it will propose to configure as much as possible automatically. This should be largely fine, but be careful when the script proposes to add environment variables to your ~/.bashrc file, since the steps below will still modify those variables.

Configure internet access and mirror sites:

cpan[1]> o conf init connect_to_internet_ok urllist

Set the install base, i.e., directory created above:

cpan[2]> o conf makepl_arg INSTALL_BASE=${VSC_DATA}/perl5

Set the preference directory path:

cpan[3]> o conf prefs_dir ${VSC_HOME}/.cpan/prefs

Commit changes so that they are stored in ~/.cpan/CPAN/MyConfig.pm, i.e.,
```
cpan[4]> o conf commit
```
Quit cpan:
```
cpan[5]> q
```

Now Perl packages can be installed easily, e.g.,

$ cpan Acme::Meta

Note that this will install all dependencies as needed, though you may be prompted.

In order to make Perl pick up your locally installed packages, execute

$ export PERL5LIB=${VSC_DATA}/perl5/lib/perl5:${PERL5LIB}
$ export PATH=${VSC_DATA}/perl5/bin:${PATH}

After this you can use locally installed packages

$ perl -e "use Acme::Meta"