mouseHole
github.com/whymirror/mousehole
Repository
whymirror/mouseholeFork
the scriptable, rewriting proxy for ruby
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
MouseHole is a personal web proxy written in Ruby designed to be simple to script. Scripts can rewrite the web as you view it, altering content and behavior as you browse. Basically, it’s an alternative to Greasemonkey, which does similar things from inside the Firefox web browser.