Genius! Madness!
This is such a good idea I'm jealous I didn't have it. No, wait. It's so mind-boggingly hackish I'm glad... Whatever, it's just a very cool hack.
I'll play with it and see how I can make the buffer extension work with it. Current implementation of the module (not on CPAN yet) features a somewhat simpler approach that requires that a match stays exactly the same before and after a buffer extension. Thus, if the user is knowledgeable to use regexes that match delimiters shorter than what they set as the block to read per buffer extension, they're *fairly* safe.
Anyway, I like the ${} approach better even if it's not going to work well. Just for the weirdness of it. :-)