While I agree installing multiple versions of Perl is a good thing, I don't agree with your naming scheme. /usr/local/bin/perl for 5.8.2 next to /usr/bin/perl for the older version seems like a good idea, but it doesn't scale. Perhaps after a year you need 5.10, of 5.8.6; where are you going to place that? I would suggest something like: /opt/perl/5.005_03, /opt/perl/5.6.1, /opt/perl/5.8.2, etc. Just a separate dir for each versions of Perl you have in use, and all a subdir from a common dir.

Alternatively, if you have a machine that has just a few applications installed, you could make Perl part of the application itself. Say, the application installs itself in /opt/my_app, just install the required version of Perl somewhere below /opt/my_app; this gives the application full control over which version of Perl is being used. I've succesfully used that technique myself in the past (for both Perl and Java), and it works like a charm.

Abigail