In my environment, I prefer to specify 'feature' rather than 'version' in part because it is much easier to specify correctly. When a module fails due to compatibility issues, 'feature' helps a maintenance programmer modify the module for an older perl. (If he choses to upgrade perl, he will probably upgrade to the newest version and not care about what is the oldest one he can get away with.) I do understand that 'version' is required by many development tools. That does not apply to me - at least not yet.