perhaps stupid suggestion, but shouldn't the polyfills be injected before any other JS-from-server being run (not after)? Is there a way to first inject the polyfills and then load the page, without "erasing" them? Hmmm tricky. Perhaps fetch the page, even with errors. Then insert the polyfills. Then initiate a re-run which will already have the poly-fills added. The latter perhaps with triggering an event or running a JS function. My first call would be to check if polyfills can be run OK with your current setup. Make a local html test file and load them in WWW::Mechanize::*. If test is successful then you may have a way to solve your problem.

bw, bliako