The only thing that virtualenv does is isolate a set of libraries to use with the default system python. If you have Python 2.6 installed, but want to use Python 2.7, you're responsible for setting it up yourself.

On the other hand, perlbrew allows you to manage completely separate builds of perl, and the associated tools like cpan/cpanminus will install to whatever the currently selected Perl is.

For example, my perlbrew at work looks like this:

  % tree -L 2 ~/perl5/perlbrew
  ~/perl5/perlbrew/
  |-- Conf.pm
  |-- bin
  |   |-- cpanm
  |   `-- perlbrew
  |-- build
  |   |-- perl-5.12.3
  |   `-- perl-5.14.1
  |-- build.log
  |-- dists
  |   |-- perl-5.12.3.tar.gz
  |   `-- perl-5.14.1.tar.gz
  |-- etc
  |   |-- bashrc
  |   `-- cshrc
  `-- perls
      |-- current -> perl-5.12.3
      |-- perl-5.12.3
      `-- perl-5.14.1

You source the appropriate ~/perl5/perlbrew/etc/{bash,csh}rc for your shell, which creates a shell function called perlbrew.

  % type perlbrew
  perlbrew is a shell function
  % perlbrew       
  Usage:
          perlbrew <command> [options] [arguments]
  
          Commonly used commands:
              init           Initialize perlbrew environment.
              install        Install perl
              list           List installed perls
              use            Use the specified perl in current shell
              switch         Permanently use the specified perl as default
              mirror         Pick a preferred mirror site
              off            Permanently turn off perlbrew
              version        Display version
              help           Read more detailed instructions
  
          Examples:
              perlbrew install perl-5.12.3
              perlbrew install perl-5.13.6
  
              perlbrew list
  
              perlbrew use perl-5.13.6
              perlbrew switch perl-5.12.3
  
              perlbrew switch /path/to/special/perl
              perlbrew switch /path/to/special/perl special-perl
              # later
  % perlbrew list                                                                                                              
  * perl-5.12.3
    perl-5.14.1
    /usr/local/bin/perl (5.8.8)
    /usr/bin/perl (5.8.8)
  % perlbrew version
  ~/perl5/perlbrew/bin/perlbrew  - App::perlbrew/0.19
  % perlbrew available
    perl-5.15.1
  i perl-5.14.1
    perl-5.12.4
    perl-5.10.1
    perl-5.8.9
    perl-5.6.2
    perl5.005_04
    perl5.004_05
    perl5.003_07
  % perlbrew install perl-5.10.1
  Attempting to load conf from ~/perl5/perlbrew/Conf.pm
  Fetching perl-5.10.1 as ~/perl5/perlbrew/dists/perl-5.10.1.tar.gz
  Installing perl-5.10.1 into ~/perl5/perlbrew/perls/perl-5.10.1
  This could take a while. You can run the following command on another shell
  to track the status:
  
    tail -f ~/perl5/perlbrew/build.log
  
  (cd ~/perl5/perlbrew/build; tar xzf ~/perl5/perlbrew/dists/perl-5.10.1.tar.gz;
    cd ~/perl5/perlbrew/build/perl-5.10.1;rm -f config.sh Policy.sh;patchperl;
    sh Configure -de '-Dprefix=~/perl5/perlbrew/perls/perl-5.10.1';make ;make
    test_harness && make install) >> '~/perl5/perlbrew/build.log' 2>&1
  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