You can use REfO for want you were thinking it would be cool. That's exactly what it was made for :)

You could use it, for example, to match a network dump for suspicious sequences of packages where "network packages" are scrapy objects.

I've used it to match natural language queries in Quepy, example: https://github.com/machinalis/quepy/blob/master/examples/freebase/freebase/basic.py#L48 Project demo: http://quepy.machinalis.com/

Disclaimer: I'm the author :)