I use this all the time to make sure I haven't stupidly added "warnings" to something that's supposed to work on 5.004. It's a simple-seeming task, but there are lots of annoying things to consider... and this code will consider them for you.
This is a fantastic tool for quickly checking how backwards compatible your code is. It's great for catching all the syntaxt that drifts in by habit (e.g. "use warnings") that gets in the way of backwards compatibility.