One of the nice things about Perl is that it’s so entrenched in the Unix toolchain that it’s very, very rare to find oneself on a machine that doesn’t have it. But that boon comes with a slip-side. Because it’s generally part of the core system, we’re usually stuck with what is there. If we’re lucky, it’s going to be 5.10 perl (2 year old technology. Not bleeding edge, but no rust yet), but chances are it’s more going to be vintage 5.8 (7 year old technology). Mind you, it’s not that unusual either to have some 5.6 (venerable 10 year old technology) still running around.
But dealing with old perls isn’t too bad. Where it gets aggravating is when you badly need a CPAN module. The obstacles standing between you and the installation of the module can be manifold. You probably don’t have the
sudo keys to the machine. Or there might be a policy in place not to upgrade any modules without calling the Council of Elrond. Or there might be a policy to only install modules only via official rpm or deb packages, which are likely to either lag behind CPAN or just not bundle the module you so badly want.
Brewing our own perl
Fortunately, there’s a way out. App::perlbrew is a tool that simplifies down to triviality the process of making local perl installations. With it, any user can, in the span of a few minutes, have a working
perl that is totally independant of whatever the system has. This is a win for you — you’re now in control of your
perl, and of your destiny — as well as for the sysadmin, who is now free of the prickly choice between system integrity and users’ happiness.
The path to self-sufficient brewing is incredibly easy. First, you have to download and install
$ curl -L https://xrl.us/perlbrewinstall | bash ## Download the latest perlbrew ## Installing The perlbrew is installed as: /home/che/perl5/perlbrew/bin/perlbrew You may trash the downloaded /tmp/perlbrew from now on. Next, if this is the first time you install perlbrew, run: /home/che/perl5/perlbrew/bin/perlbrew init And follow the instruction on screen. ## Done. (automatically removes downloaded /tmp/perlbrew)
perlbrew under the
perl5 directory in your home. That
perl5 directory, incidently, will be where all the Perl installations will go. That’s very convenient to clone your Perl install on other machines (provided it’s the same architecture, ‘
scp -r ~/perl5 che@othermachine:perl5‘ and you’re done), or to clean up after yourself (the sysadmin wasn’t too keen on having rogue perls on the machine after all? lucky you, you’re one ‘
rm -fr ~/perl5‘ away from total denialibility).
Anyway, back to the installation. The next step is to tweak our environment to use the perls that will be provided by
perlbrew. To do that, we follow
perlbrew‘s instructions. First we do:
$ /home/che/perl5/perlbrew/bin/perlbrew init Perlbrew environment initiated, required directories are created under /home/che/perl5/perlbrew Well-done! Congratulations! Please add the following line to the end of your ~/.bashrc source /home/che/perl5/perlbrew/etc/bashrc After that, exit this shell, start a new one, and install some fresh perls: perlbrew install perl-5.12.1 perlbrew install perl-5.10.1 For further instructions, simply run: perlbrew The default help messages will popup and tell you what to do! Enjoy perlbrew at $HOME!!
And then we add
~/.bashrc. You can look at the file if you are curious. It’s not doing anything more nefarious than to tweak your
$PATH and a few other environment variables.
With that, the
perlbrew environment is ready and installed. Now let’s populate it with a few perls. First, let’s get the latest and greatest:
$ perlbrew install perl-5.12.3 Attempting to load conf from /home/che/perl5/perlbrew/Conf.pm Fetching perl-5.12.3 as /home/che/perl5/perlbrew/dists/perl-5.12.3.tar.gz Installing perl-5.12.3 into /home/che/perl5/perlbrew/perls/perl-5.12.3 This could take a while. You can run the following command on another shell to track the status: tail -f /home/che/perl5/perlbrew/build.log (cd /home/che/perl5/perlbrew/build; tar xzf /home/che/perl5/perlbrew/dists/perl-5.12.3.tar.gz;cd /home/che/perl5/perlbrew/build/perl-5.12.3;rm -f config.sh Policy.sh;sh Configure -de '-Dprefix=/home/che/perl5/perlbrew/perls/perl-5.12.3';make;make test && make install) >> '/home/che/perl5/perlbrew/build.log' 2>&1 Installed perl-5.12.3 as perl-5.12.3 successfully. Run the following command to switch to it. perlbrew switch perl-5.12.3
and, why not?, an older one, just in case we want to run our code against a version matching what we have in our production environment:
$ perlbrew install perl-5.10.1 Attempting to load conf from /home/che/perl5/perlbrew/Conf.pm Fetching perl-5.10.1 as /home/che/perl5/perlbrew/dists/perl-5.10.1.tar.gz [ yadah yadah yadah... ] Installed perl-5.10.1 as perl-5.10.1 successfully. Run the following command to switch to it. perlbrew switch perl-5.10.1
We’ll stop here for the time being, but we could install every version of Perl of the last 10 years, and cackle like loons as we’d have thus built the ultimate development environment. The fun doesn’t even stop there: we can also build development versions of perl, and build perls of the same version, but with different building arguments (with/without threads, for example).
Anyway, for the time being, we have two local perls built, plus the system-wide perl. We can see then by doing:
$ perlbrew list perl-5.10.1 perl-5.12.3 * /usr/bin/perl (5.10.1)
And switching to one of our home-cooked version is as simple as doing:
$ perlbrew switch perl-5.10.1 $ which perl /home/che/perl5/perlbrew/perls/perl-5.10.1/bin/perl che@enkidu:~$ perl -v This is perl, v5.10.1 (*) built for i686-linux [..] $ perlbrew switch perl-5.12.3 $ perl -v This is perl 5, version 12, subversion 3 (v5.12.3) built for i686-linux [..]
Want to revert to the system perl for a moment? That’s not too hard either:
$ perlbrew off
Spicing up the brew with CPAN spiffiness
With our own perl, we are now free to install whichever module we want without fear of impacting anybody but us. The classical installation process would make us use
cpan from CPAN or
cpanp from CPANPLUS. Those interfaces to CPAN (the archive) are true and tried, but their extensive configuration can be a little daunting. There is work being done to make them a little more streamlined, but in the meantime there is a third offering, App::cpanminus, which is optimized for simplicity.
cpanm, we’ll leverage our brand-new shiny
$ perlbrew install-cpanm
Done. No, seriously, we’re done.
cpanm can now be used to install all the modules you want. If those modules have dependencies, they will automatically be followed and installed:
$ cpanm XML::LibXML --> Working on XML::LibXML Fetching https://search.cpan.org/CPAN/authors/id/P/PA/PAJAS/XML-LibXML-1.70.tar.gz ... OK Configuring XML-LibXML-1.70 ... OK ==> Found dependencies: XML::SAX, XML::NamespaceSupport --> Working on XML::SAX Fetching https://search.cpan.org/CPAN/authors/id/G/GR/GRANTM/XML-SAX-0.96.tar.gz ... OK Configuring XML-SAX-0.96 ... OK ==> Found dependencies: XML::NamespaceSupport --> Working on XML::NamespaceSupport Fetching https://search.cpan.org/CPAN/authors/id/P/PE/PERIGRIN/XML-NamespaceSupport-1.11.tar.gz ... OK Configuring XML-NamespaceSupport-1.11 ... OK Building and testing XML-NamespaceSupport-1.11 ... OK Successfully installed XML-NamespaceSupport-1.11 Building and testing XML-SAX-0.96 ... OK Successfully installed XML-SAX-0.96 Building and testing XML-LibXML-1.70 ... OK Successfully installed XML-LibXML-1.70
cpanm can take a list of module as arguments, or can read them from STDIN, which means you can make a list of your favorite modules and, on any brand-new machine do
$ cpanm < my_favorite_modules.txt
to get your full armory installed. Or, for extra-hardcore bonus points, you could keep your list of favorite modules as a CPAN module and do
$ cpanm Task::BeLike::YANICK
But the point is, you now have the power to leverage the power of modern Perl, no matter where you are. Huzzah!