How can I install specialized environments for different Perl applications?

Question

Is there anything equivalent or close in terms of functionality to Python\'s virtualenv, but for Perl?

I\'ve done some development in Python and a possibility of having

Answer 1

While investigating, I discovered this and some other pages (this one is too old and misses new technologies, this reddit post is a slight misdirect).

The problem with perlbrew and plenv is that they seem to be replacements for pyenv, not virtualenv. As noted here pyenv is for managing python versions, virtualenv is for managing per-project module versions. So, yes, in some ways similar to local::lib, but with better usability.

I've not seen a proper answer to this question yet, but from what I've read, it looks like the best solution is something along the lines of:

• Perl version management: plenv/perlbrew (with most people favouring the more contemporary bash based plenv over the perl based perlbrew from what I can see)
• Module version management: Carton
• Module installation: cpan (well, cpanminus anyway, ymmv)

To be honest, this is not an ideal set up, although I'm still learning, so it may yet be superior. It just doesn't feel right. It certainly isn't a like for like replacement for virtualenv.

There are a couple of posts I've found saying "it is possible" but neither has gone any further.

Answer 2

What I do is start the CPAN shell (cpan) and install my own Perl 5.10 from it (I believe the command is install perl-5.10). This will ask for various configuration settings; I make sure to make it point to paths under /usr/local (or some other installation location other than the default).

Then I put its resulting location in my executable $PATH before the standard perl, and use its CPAN shell to install the modules I need (usually, a lot). My Perl scripts all start with the line

#!/usr/bin/env perl

Never had a problem with this approach.

Answer 3

Programs can modify what directories they check for libraries uwith use lib. This lib directory can be relative to the current directory. Libraries from these directories will be used before system libraries, as they are placed at the beginning of the @INC array.

I believe cpan can also install libraries to specific directories. Granted, cpan draws from the CPAN site in order to install things, so this may not be the best option.

Answer 4

Also checkout perl-virtualenv , this seems to be wrapper around local::lib as suggested by Hobbs, but creates a bin/activate and bin/deactivate so you can use it just like the python tool.

I've been using it quite successfully for a month or so without realising it wasn't as standards as perhaps it should be.

It makes it lot easier to set up a working virtualenv for perl as while local:lib will tell you what variables you need to set, etc. perl-virtualenv creates an activate script which does it for you.

Answer 5

It looks like you just need to use the INSTALL_BASE configuration for Makefile.PL (or the --install_base option for Build.PL)? What exactly do you need the solution to do for you? It sounds like you just need to get the installed module in the right place. You've presented your problem as an XY Problem by specifying what you think is the solution is rather than letting us help you with your task.

See How do I keep my own module/library directory? in perlfaq8, for instance.

If you are downloading modules from CPAN, the latest cpan command (in App::Cpan) has a -j switch to allow you to choose alternate CPAN.pm configuration files. In those configuration files you can set the CPAN.pm options to install wherever you like.

Based on your clarification, it sounds like local::lib might work for you in single, simple cases, but I do this for industrial strength deployments where I set up custom, private CPANs per application, and install directly from those custom CPANs. See my MyCPAN::App::DPAN module, for instance. From that, I use custom CPAN.pm configs that analyze their environment and set the proper values to each application can install everything in a directory just for that application.

You might also consider distributing your application as a Task::. You install it like any other Perl module, but dependencies share that same setup (i.e. INSTALL_BASE).

Answer 6

There's a tool called local::lib that wraps up all of the work for you, much like virtualenv. It will:

• Set up @INC in the process where it's used.
• Set PERL5LIB and other such things for child processes.
• Set the right variables to convince CPAN, MakeMaker, Module::Build, etc. to install libraries and store configuration in a local directory.
• Set PATH so that installed binaries can be found.
• Print environment variables to stdout when used from the commandline so that you can put eval $(perl -Mlocal::lib) in your .profile and then mostly forget about it.