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Installing Perl Libraries

This guide explains how to install Perl modules in a non-system location (e.g., project or group directory) using cpanm and local::lib. This is ideal for environments where you cannot modify system Perl without root access, such as on RCAC clusters (Gautschi, Negishi, Bell).

  1. Create the required directory in your desired location (e.g., home or project space).

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    mkdir -p /depot/gcore/localperl
cd /depot/gcore/localperl

    You can substitute this path to any location you want (~ or even $SCRATCH) .

  2. Set up the environment to install Perl modules locally:

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    nano /depot/gcore/localperl/env.sh

    Paste the following into env.sh:

    env.sh
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    export PERL_LOCAL_LIB_ROOT=/depot/gcore/localperl
export PERL_MB_OPT="--install_base /depot/gcore/localperl"
export PERL_MM_OPT="INSTALL_BASE=/depot/gcore/localperl"
export PERL5LIB=/depot/gcore/localperl/lib/perl5:$PERL5LIB
export PATH=/depot/gcore/localperl/bin:$PATH

    Then activate it:

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    source /depot/gcore/localperl/env.sh

    Note

    You can check which Perl is in use and where it looks for libraries by running which perl and perl -V commands. Make sure it points to /usr/bin/perl and includes /depot/gcore/localperl/lib/perl5 in @INC after activating your environment.

  3. Install cpanm (Perl module installer) into the custom location:

    Warning

    Make sure you've already run source /depot/gcore/localperl/env.sh before installing modules with cpanm, or they will be installed in the wrong location.

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    curl -L https://cpanmin.us | perl - --local-lib=/depot/gcore/localperl App::cpanminus

    Confirm that it worked:

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    which cpanm
# should return: /depot/gcore/localperl/bin/cpanm

  4. Install the required Perl modules:

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    cpanm DateTime namespace::autoclean Sub::Name \
      JSON Getopt::Long Pod::Usage JSON::XS Mojolicious

    You can add more modules as needed.

  5. (Optional) Automatically load your environment in future sessions:

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    echo 'source /depot/gcore/localperl/env.sh' >> ~/.bashrc

    If you prefer not to modify your ~/.bashrc, you can manually source the environment script each time you start a new session.

    Warning

    Remember to run source /depot/gcore/localperl/env.sh in any new shell before running scripts that depend on these local modules.

Testing the installation

To verify that the installation was successful, you can run a simple Perl script that uses one of the installed modules:

test_perl_modules.pl
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#!/usr/bin/perl
use strict;
use warnings;
use DateTime;
use JSON;

print "Local Perl modules are working!\n";

Run the script:

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perl test_perl_modules.pl

If you see the message "Local Perl modules are working!", your installation is successful.

FAQs

How can I get a list of all installed perl modules?

You can use the following command to list all installed Perl modules:

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perldoc perllocal

or

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find /depot/gcore/localperl/lib/perl5 -name '*.pm'