Backward compatibility is a concern.  However, having the flags test true when present, which they don't currently, should be considered a bug fix, I think.

So, I added a some tests to confirm the current behavior, and wrote a new patch that *just* fixes the 'test true if present' bug, leaving the other behaviors unchanged.  Reviews appreciated.  And if anyone can think of tests I missed, please let me know; I'm a little nervous about the regex change (I hate dealing with regexes :)

This issue was originally about other bugs as well, but I'm changing the title to reflect just this fix.  If there are still other remaining bugs, please open a new issues for them.

Thanks for the patch, Julien.  Although I didn't use your code, it did inform my work.