Checks if the environment (PATH etc.) is compatible with the Perl that is pointed to by the symbolic link.

What do you mean by an environment being compatible with a version of Perl?

How about the following situation: Keep your /app/perl/VERSION/ structure. Let /usr/bin/perl be a symbolic link to newest perl (for instance /app/perl/5.8.2/bin/perl). Developers use #!/usr/bin/perl by default. If you need a roll-back, change the first line to #!/app/perl/WHATEVER/bin/perl.

So, developers don't need to do anything if a new version of perl gets installed, unless a new version breaks their program. Then they only have to perform a one line fix for each program that breaks. I'm not sure you are looking for a way to automatically detect whether scripts will fail and then fallback, but that's something I wouldn't do myself.

Abigail