In this article we'll discuss how to organize your libraries and following the best practices these days to avoid installing new cpan modules as root. This way you can always test your applications and experiment with the latest versions of some modules without being afraid that you can screw something.

Before we start, we should say a few words about cpanminus and local::lib. cpanminus is a great script to get, unpack, build and install modules from CPAN and local::lib is a greet tool to create and use local lib/ for perl modules.

Installing modules locally has never been easier. First we need to install App::cpanminus and local::lib locally:

  curl -L http://cpanmin.us | perl - -l ~/perl5 App::cpanminus local::lib

This will install either cpanminus and local::lib (and all other required modules) locally into $HOME/perl5 directory.

Now all we need to do is now to specify the appropriate environment variables to tell Perl where to look for installed modules.

  eval `perl -I ~/perl5/lib/perl5 -Mlocal::lib=~/perl5`
  echo 'eval $(perl -I$HOME/perl5/lib/perl5 -Mlocal::lib)' >> ~/.bashrc

It's time to install Catalyst locally:

 dpetrov@vaio:~$ cpanm Catalyst Catalyst::Devel

perlbrew is incredible easy to use Perl Environment manager which lets you to manage different Perl installations in your $HOME. This could be useful if you don't want to upgrade your system Perl or you would like to test your code behavior under different Perl versions.

Assuming that you've already installed cpanminus let's brew some of the latest Perl versions.

First we need to insall App::perlbrew:

  dpetrov@vaio:~$ cpanm App::perlbrew
  --> Working on App::perlbrew
  ...
  Successfully installed App-perlbrew-0.33
  28 distributions installed

Than we need to init perlbrew:

  dpetrov@vaio:~$ perlbrew init
  ...
  Enjoy perlbrew at $HOME!!

We can take a look to all available Perl versions:

  dpetrov@vaio:~$ perlbrew available
  perl-5.15.5
  perl-5.14.2
  ...

And finally we can brew the some of the latest available Perl versions.

  dpetrov@vaio:~$ perlbrew install 5.14.2
  ...

Since that could take a while you can probably go and grab a cup of coffee :) Once the new Perl version is installed we can switch and verify that:

  dpetrov@vaio:~$ perlbrew use perl-5.14.2
  A sub-shell is launched with perl-5.14.2 as the activated perl. Run 'exit'
  to finish it.

  dpetrov@vaio:~$ perl -v
  This is perl 5, version 14, subversion 2 (v5.14.2) built for x86_64-linux

Now you can enjoy using perl 5.14.2 and you can switch back to the system Perl version simply by turning perlbrew off.

We should mention that local::lib was not designed to work with multiple Perl versions. That's so because usually XS modules are not compatible across major Perl releases. That's usually not such a big issue, because using perlbrew you have your own Perl, which allows you to install different module versions across different Perl versions (and all that is locally).

Perlbrew, local::lib and cpanminus are some awesome tools which can be really helpful during your development. They are extremely helpful if you don't have root access or you don't want to deal with all your modules locally. In addition you can always use something like App::cpanoutdated and test your codebase against latest modules releases simple like that:

  cpanm App::cpanoutdated
  cpan-outdated | cpanm

and if something goes wrong you can always start from scratch: rm -r ~/perl5

Dimitar Petrov <mitakaa@gmail.com>