SPUG: How do *you* install multiple versions of Perl?

[Michael R. Wolf]

As a follow-up to the Josh's (general, theoretical) talk last night on  
Perl 5.12, I'd like to pose a (specific, practical) question:
   How do you install and use multiple versions of Perl on a single  
machine?

I'm interested because, even 2 years after its introduction, Perl 5.10  
is still not common in many environments (default OS installations,  
web hosting services, corporate IT environments, etc).  I'm guessing  
(based on my own experience) that it's often easier for folks not on  
the cutting edge to use the given version of Perl (usually 5.8)  
instead of stepping up to a newer one.

Perhaps sharing how you do it would encourage others to do so.

Here are some important issues to address when installing a 2nd (or  
10th) version of Perl on a machine.  How do you handle them in your  
environments?
  - Code that depends on the current version of Perl MUST continue to  
work
  - OS processes MUST use the version of Perl shipped with the OS (or  
risk breaking, not really an option)
  - New code CANNOT use the installed version of Perl, since it's  
exercising new features
  - The new and old Perl versions MAY share core modules or add-ons  
(e.g. from CPAN)
  - Laptop users MIGHT BE their own administrators, but MIGHT NOT BE
  - Corporate environments are often designed for stability, not  
flexibility.
  - Various she-bang constructs MIGHT dictate or suggest a particular  
version
  - Command-line arguments and paths MIGHT do so, too
  - Library search can be controlled via 'use directory' or by setting  
PERL5LIB
  - Library structure is contained in directories, some of which may  
be symlinks


So... if you have BCP's (Best Current Practices) or even illustrative  
failures, please it to encourage a wider experimentation with newer  
versions of Perl.  It would be great to get a broad mix of answers:
  - Windows and *nix
  - development and deployment
  - laptop and server

Thanks for sharing...

-- 
Michael R. Wolf
     All mammals learn by playing!
         MichaelRWolf at att.net