Some are really difficult to overcome, such as building an older release on a newer platform.

If the situation here is as I understand it, I believe that it involves older releases installed long ago on older platforms, with no will to install newer releases for whatever reason. Managers can be "funny" that way and I have had to deal with similar situations in the past.

So the code here needs to run on many Perl versions, from 5.8 to 5.32 or so, whatever the various machines in $WORK's fleet have installed.