title: Should I output warnings to STDERR or STDOUT?
body: <p>I'm making a script that handles a predefined set of data, outputting to a file. I want to pop up a warning when one datum (which is always "Regular" in every set that I've had access to) is different stating that this value is unhandled (since I don't know how it affects the data). Should I output this warning to stderr or stdout?</p>