Flavio Poletti bio photo

Flavio Poletti

Irreducible Perler.

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local::lib is a love-it-or-hate-it module, with the additional feature that you don’t get the hate-it part.

Recently, I had to develop a script to do a couple of HTTP redirections. I headed towards CPAN, quickly found that HTTP::Server::Simple (and in particular HTTP::Server::Simple::CGI) and in some twenty minutes I had a working prototype. Forget that I changed my mind a couple of times before having what I eventually used for my test…

Now, I knew I had to go into an environment that could possibly prevent me from using my machine to perform the test. As a matter of fact, I didn’t know whether I could use the program anywhere, let alone know what kind of Perl environment I would have found. Nightmare!

Luckily enough, it turned out that I only needed modules that do not require compilation. I love Pure Perl modules! So now I had the problem to bundle all the needed non-core modules in a way that was convenient to deliver. This is where local::lib really saved the day, and in particular its --self-contained option. Well - yes - I’ve seen options that were commented way better… but at least the only reference in the synopsis made me curious enough to discover that it was hitting the nail right in the head.

On my machine I have my own compiled Perl version to tinker with, so I installed local::lib without the need to bootstrap anything. At this point, all I had to do was something along these lines:

shell$ perl -MCPAN -Mlocal::lib=--self-contained,my_lib -e 'CPAN::install($_) for @ARGV' HTTP::Server::Simple URI Log::Log4perl

Yes… I’m quite fond of Log::Log4perl, but that’s another story.

The installation above went smooth and installed all the modules, and their needed non-core dependencies, under the directory tree starting from my_lib. I checked that there were actually no compiled components - dependencies could play some trick - and I verified that I had been lucky. Yay!

The directory structure you end up with is more or less the following:


I didn’t need either the bin or the man subdirectory, so I just moved the contents my_lib/lib/perl5 into a lib subdirectory, removed what remained of my_lib and… that’s it! Well, wait a minute, I had to make a slight change to the code as well:

use FindBin;
use lib $FindBin::Bin;

OK, now that’s it! The funny part? I was actually able to use my laptop, so I didn’t need anything of this…