I'm aware of how to do this with Python, that won't solve the issue in an ideal way for me. Introducing Python is uncomfortably outside of the scope of what I'm writing.
I'm attempting to use a texture lookup from within OSL, as part of a tutorial I'm creating; but the default working directory is the same as Blender's. That makes it very difficult to write portable code that will work on any other machine--I can't use relative paths. I'm really trying to ensure that the tutorial file will immediately work on 2.92, on any machine, out-of-the-box.
Is there a manner in which OSL can retrieve the path to the current .blend file internally?