You are right that it is a source code filter (albeit one that is portable all the way back to at least perl 5.005_04). But would you extend your remarks on why you believe that that of itself is a good reason to not release it? I have tried to deliberately create a syntax that cannot be easily 'triggered' by accident or mis-parse in a way that generates false line numbered errors. If a particular line in the original causes an error - that will be the line the compiler reports after processing as having generated the error. And a module has to intentionally use it - so it isn't like a random module will be "side-swiped" by it.

So what, specifically, do you find objectionable about the use of source code filters?