I have never had to manage thousands of Perl scripts, but I have managed hundreds of applications on hundreds of servers and many hundreds of workstations of diverse OS and I have almost always installed perl - perl and everything else locally. One can install multiple versions of perl on a system, in case all the Perl scripts cannot be upgrade to work on the same version of perl, allowing you to upgrade incrementally.

I have rarely used network drives for executeables and libraries and generally prefer automated system builds and automated software distribution to replicate consistent configurations of software locally onto multiple systems. The shared resource significantly increases the interdependence between systems and turns every little upgrade into a major event requiring weeks to months of testing.

I wouldn't be interested in dynamically editing the Perl scripts at run time on a per platform basis or per system basis (there can be many relevant differences between systems, even where the OS is the same). If I really felt compelled to share Perl scripts across diverse platforms, I would probably write platform specific wrapper scripts that executed the shared Perl scripts appropriately, so that the shebang lines in the shared scripts were irrelevant. Windows and *nix are different enough that it may not be as simple as rewriting the shebang line. But I wouldn't much like to do this either: I would, as much as possible, move the shared code into platform independent modules and write minimal / trivial platform specific scripts to load and run the modules.

I'm lazy and find that I get much more sleep when systems are simple and, as much as possible, consistent but independent so that the scope of problems and changes are small. This isn't to suggest that common solutions aren't advantageous. I use standardized system builds (automated installs and system cloning) almost exclusively for the 'platform' and common software and only install unique software on a case by case basis. Diversity isn't always your enemy but I tolerate it only where there are specific justifications.

This isn't to suggest that a shared resource of perl executeables and libraries couldn't be achieved or that for people smarter than me that it might not be easy and manageable.