in reply to I'm looking for a one-liner filter 'twixt two regexes

like everyone else, I'm not 100% sure I understand what you want. But if it's just to print out the lines between a start and a stop regexp, wouldn't this do the trick?
perl -ne 'print if /start/ .. /end/' *.html
Note that this will not allow /start/ and /end/ to be on the same line. If you want that as an option, you need to replace the .. operator with ....

See man perlop.

-- Dan