Right now, there aren't any differences because we've just been lucky enough to not experience any changes in the versions we've implemented in the current common.pm files. However, if I were to go back and implement them for the older versions, there would definitely be differences in the modules used and even the implementation of the same modules.
Example: I use Date::Manip for almost all of my date handling, but the module for perl < 5.10 is significantly different than perl >= 5.10.
Loading completely different modules in one version over another is definitely a scenario I will run across as well.
I'll check out the post you provided. Thanks.