How to Install Perlbrew and Manage Multiple Versions of Perl 5 on CentOS 7

Introduction

Perl 5 is a mature, full-featured programming language. It’s used in production projects of all types, including mission critical business systems all over the world. The Perlbrew software package lets you install, remove, and switch between versions of the Perl 5 programming language.

Perlbrew installs Perl in your home directory, and each version of Perl you install is independent from the others. This lets you test your code against multiple Perl versions without interfering with, or being influenced by, any other version. This includes your operating system’s default Perl package, which is typically much older than the latest stable version.

In this tutorial, you’ll install Perlbrew and use it to install and test a version of Perl 5.

Prerequisites

To follow along with this guide you’ll need:

• One CentOS 7 server set up by following the CentOS 7 initial server setup guide, including a sudo non-root user and a firewall.

Step 1 – Installing Perlbrew

Before you install Perlbrew, you’ll need a few prerequisite packages. Perlbrew needs gcc, a compiler, and bzip2, a compression utility, in order to compile and install Perl. These packages are not installed by default on CentOS 7, but if you have added some packages to your server, you may already have these two packages. You can find out what you’re missing easily enough.

Building Perl requires two gcc-related packages, libgcc and gcc. To see if you already have these packages, execute the following command:

rpm -qa | grep gcc

If they’re installed, you’ll see the following output:

Is the gcc package installed?
libgcc-4.8.5-11.el7.x86_64
gcc-4.8.5-11.el7.x86_64

CentOS 7 only includes the libgcc package by default, so you can install gcc with the following command:

sudo yum install gcc 

You also need the bzip2-libs and bzip2 packages. Check to see that they’re installed as well:

rpm -qa | grep bzip2

If they’re both installed, you’ll see the following:

Is the bzip2 package installed?
bzip2-libs-1.0.6-13.el7.x86_64
bzip2-1.0.6-13.el7.x86_64

By default, CentOS 7 only includes the bzip2-libs package. Add the bzip2 package:

sudo yum install bzip2 

Finally, install the patch utility.

sudo yum install patch

With the prerequisites out of the way, you can install Perlbrew. Download the installation script to your server:

curl -L https://install.perlbrew.pl -o install.perlbrew.pl

To audit the contents of the script before running it, open it in a text editor to view its contents:

vi install.perlbrew.pl

Once you’re comfortable with the script’s contents, pipe the script to bash to run the installation script:

cat install.perlbrew.pl | bash

This will create a new directory structure in /home/sammy/perl5, where Perlbrew will store its support files and versions of Perl. You’ll see the following output from the installation script:

Output
## Download the latest perlbrew

## Installing perlbrew
perlbrew is installed: ~/perl5/perlbrew/bin/perlbrew

perlbrew root (~/perl5/perlbrew) is initialized.

Append the following piece of code to the end of your ~/.bash_profile and start a
new shell, perlbrew should be up and fully functional from there:

    source ~/perl5/perlbrew/etc/bashrc

Simply run `perlbrew` for usage details.

Happy brewing!

## Installing patchperl

## Done.

Next, use the perlbrew utility to create some initial configuration files and directories in /home/sammy/perl5/perlbrew:

~/perl5/perlbrew/bin/perlbrew self-install

You’ll see the following output:

Output
You are already running the installed perlbrew:
    /home/sammy/perl5/perlbrew/bin/perlbrew

Perlbrew is now installed, but you’ll want to modify your shell’s configuration files to make it easier to use.

Step 2 – Editing Your .bash_profile to Include Perlbrew

Before using Perlbrew to install a version of Perl, you should edit your .bash_profile file so it automatically sets some important Perlbrew environment variables. Perlbrew makes this easy by including the needed code in another configuration file which you can include in your .bash_profile.

Open the file ~/.bash_profile in your editor:

vi ~/.bash_profile

Add the following line at the bottom of the file to include the Perlbrew settings:

source ~/perl5/perlbrew/etc/bashrc

Save the file and exit the editor.

Then log out and then log back in to ensure that your .bash_profile file loads Perlbrew’s settings. It will now add /home/sammy/perl5/perlbrew/bin to the front of your PATH environment variable, and set some other environment variables Perlbrew needs.

Verify that these environment variables have been set by running the env command and filtering the results with grep for the text PERL:

env | grep PERL                                                                                                                  

You should see entries similar to the following:

Output
PERLBREW_BASHRC_VERSION=0.78  
PERLBREW_ROOT=/home/sammy/perl5/perlbrew
PERLBREW_HOME=/home/sammy/.perlbrew

These environment variables tell Perlbrew where important directories are located. The version number may be higher if Perlbrew was revised after this tutorial was published.

Typing which perlbrew should now identify the full path to the perlbrew command:

which perlbrew

You should see the following in your terminal:

Expected Output
~/perl5/perlbrew/bin/perlbrew

Now that Perlbrew is installed and configured, let’s start using it.

Step 3 – Installing and Building Your Perl Version.

Let’s use Perlbrew to install a stable version of Perl 5. Use the perlbrew command to see which Perl versions are available for installation:

perlbrew available

You’ll see a listing similar to the following partial listing:

Partial Listing
  perl-5.25.11
  perl-5.24.1
  perl-5.22.3
  perl-5.20.3
  perl-5.18.4
  ...

Odd-numbered major versions, such as perl-5.25, are under active development and are not considered stable or production-ready. In general, you won’t use versions older than 5.10.1 unless you have legacy code that requires one of these older versions.

According to the output, perl-5.24.1 is the most recent stable version, as it has the largest even major number. You can pick any Perl version shown in the list, but for this tutorial, we’ll install perl-5.24.1.

Install it with perlbrew install:

perlbrew install perl-5.24.1

The Perl installation can take quite a while to build and install, generally about 20 minutes. Do not interrupt the build process. If you want to see the build’s progress, you can open a separate terminal session and monitor the build log with tail -f ~/perl5/perlbrew/build.perl-5.24.1.log.

After the build completes, you will see the following output from Perlbrew:

[secondary_label Output] 
perl-5.24.1 is successfully installed.

When the build completes, the last line of the build log file will be:

Output
##### Brew Finished #####

You can repeat this process for each version of Perl you want to install. This guide only demonstrates installing one version, but this step can be repeated for as many versions as you need.

Next, let’s look at how to use Perlbrew to work with multiple versions of Perl.

Step 4 – Managing Your New Perl Installation

At this point there are two versions of Perl on your system: the vendor version provided with the operating system, and the Perl version you just installed within the ~/perl5 directory with Perlbrew.

To use your new Perl installation, run the following command:

perlbrew use perl-5.24.1

This command updates the PERLBREW_PERL environment variable to point to the specified Perl version for your current login session.

If you want a version of Perl to be your default each time you log in, run this command:

perlbrew switch perl-5.24.1

This command sets the PERLBREW_PERL environment variable to point to the specified Perl version every time you log in.

Verify that you’re now using Perl 5.24.1:

perl -V

You should see the following output:

Parial Output
...
%ENV:
    PERLBREW_BASHRC_VERSION="0.78"
    PERLBREW_HOME="/home/sammy/.perlbrew"
    PERLBREW_MANPATH="/home/sammy/perl5/perlbrew/perls/perl-5.24.1/man"
    PERLBREW_PATH="/home/sammy/perl5/perlbrew/bin:/home/sammy/perl5/perlbrew/perls/perl-5.24.1/bin"
    PERLBREW_PERL="perl-5.24.1"
    PERLBREW_ROOT="/home/sammy/perl5/perlbrew"
    PERLBREW_VERSION="0.78"
@INC:
    /home/sammy/perl5/perlbrew/perls/perl-5.24.1/lib/site_perl/5.24.1/x86_64-linux
    /home/sammy/perl5/perlbrew/perls/perl-5.24.1/lib/site_perl/5.24.1
    /home/sammy/perl5/perlbrew/perls/perl-5.24.1/lib/5.24.1/x86_64-linux
    /home/sammy/perl5/perlbrew/perls/perl-5.24.1/lib/5.24.1
    .

Perlbrew installs just the core Perl code. To see which modules comprise the core for a particular version of Perl, execute this command:

corelist -v 5.24.1

At any time after using the perlbrew use or perlbrew switch commands, you can return to using the vendor version of Perl by using the command perlbrew off. If you used perlbrew switch to set a new default Perl, you can remove that default setting with perlbrew switch-off.

The perlbrew command, issued with no flags, generates a simple listing of helpful commands. The command perlbrew help generates more detailed help information.

Let’s install some additional Perl modules.

Step 5 – Testing Your Perl Installation by Installing Modules from CPAN

Perl provides a vast array of public code modules that extend the core language. These modules are stored in the Comprehensive Perl Archive Network (CPAN). The code you are thinking of writing may already be written, tested, and available in CPAN. You can use the CPAN repository to avoid re-inventing the wheel.

App::cpanminus is a Perl module that lets you explore the CPAN repository and download modules. It’s popular and easy to use. Let’s install this module and use it to test your new Perl installation.

Ensure you are using your new Perl installation:

perlbrew use perl-5.24.1

Install the cpanminus module with:

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

You’ll see the following output:

Output
--> Working on App::cpanminus
Fetching http://www.cpan.org/authors/id/M/MI/MIYAGAWA/App-cpanminus-1.7043.tar.gz ... OK
Configuring App-cpanminus-1.7043 ... OK
Building and testing App-cpanminus-1.7043 ... OK
Successfully installed App-cpanminus-1.7043
1 distribution installed

Verify that the cpanminus module is now present:

perlbrew list-modules

You should see App::cpanimus in the output:

Output
App::cpanminus
Perl

You can now use the command-line utility cpanm to install additional modules and their dependencies. Let’s use it to install the Email::Simple module, which you’d need if you were writing some Perl code to send email messages.

cpanm Email::Simple

When the installation is complete, review the list of modules again:

perlbrew list-modules

You’ll see the following output:

Expected Output
App::cpanminus
Email::Date::Format
Email::Simple
Perl

The Email::Simple module requires the Email:Date::Format module. The cpanm program installed the dependency for you.

If you are not sure what to install to round out your core Perl installation, take a look at Task::Kensho, which describes numerous modules addressing a wide range of tasks that are considered production-ready.

Conclusion

In this tutorial you installed Perlbrew and used it to install a local version of Perl in your home directory. You also learned how to use Perlbrew to install and manage multiple versions of Perl, and how to install additional modules from the CPAN repository with the cpanm utility. You can use the same process to install different versions of Perl 5, so you can install the version you need for your app.