Thank you choroba, Bravo!! (you went from "choroba has never used --state" to figuring the answer out rather quickly ;-)

Update: Although it seems to be not quite true that "By appending t to the command line, you told prove to run all the tests in t/ together with the failed ones." ... apparently prove skips from the directory any test files that have already been run via failed.

Since I never rely on prove's looking for t/ by default it did not occur to me that the examples in the doc are showing complete commands.

I think --state would be more useful for me if it applied to individual tests within files (and within subtests even!) Maybe a plugin is called for.