Perl

💬 Perl scripts and applications do not need installation. They can be simply downloaded and run.

☝🏻 Roihu does not have a perl module. A system Perl is available at /usr/bin/perl, but it does not include cpanm or most common libraries.

Installing Perl modules

💬 Sometimes applications may require additional modules to run.

• These “Perl modules”, should not be confused with the software modules on CSC supercomputers.

💬 You should check the installation instructions for each module. For libraries in CPAN, the easiest method is to use cpanm.

• You can check out the CPAN documentation here.

In this example, we’ll add the Perl module JSON to our own environment

1. Check if JSON is already available:

   perl -e 'use JSON;'
   

   • The error message indicates that it is not found, so you need to install it.

   🗯 By default, cpanm tries to install new modules to the Perl installation path, which will not work.

   • You need to set the location to a directory where you have write access. It could be e.g. your project’s /projappl directory.
   • This is accomplished by setting a few environment variables.

2. Replace the desired path for PERL_BASE and run the following:

   export PERL_BASE="/projappl/<project>/$USER/myperl"  # replace <project> with your CSC project, e.g. project_2001234
   export PERL_MM_OPT="INSTALL_BASE=$PERL_BASE"
   export PERL_MB_OPT="--install_base $PERL_BASE"
   export PERL5LIB="$PERL_BASE/lib/perl5"
   export PATH="$PERL_BASE/bin:$PATH"
   mkdir -p $PERL_BASE
   

3. Install cpanm (only needs to be done once):

   curl -L https://cpanmin.us | perl - App::cpanminus
   

4. You can now install the module:

   cpanm JSON
   

5. You can now try again:

   perl -e 'use JSON;'
   

   • This time there’s no error message, indicating that the JSON module is now available.

Additional info

💬 The installation only needs to be done once, but you need to always ensure Perl knows where to find the installed modules.

💭 There are three main ways to do this (we used the second already).

Option 1

• Pass the path using the command-line option -I:

  perl -I /projappl/<project>/$USER/myperl/lib/perl5 ./my_app.pl  # replace <project> with your CSC project, e.g. project_2001234
  

Option 2

• Include the path in the $PERL5LIB environment variable:

  export PERL5LIB=/projappl/<project>/$USER/myperl/lib/perl5:$PERL5LIB  # replace <project> with your CSC project, e.g. project_2001234
  

Option 3

• Include the path in your Perl script with use lib:

  use lib '/projappl/<project>/$USER/myperl/lib/perl5';
  use My::Module;