bug#68808: subsecond mtime discovery code insufficient

[Karl Berry]

(Off-topic for the original bug, but for the sake of public discussion ...)

Hi Zack,

    It is absolutely not *supposed* to be using shell arrays. 

I guess it's not an array. It's the square bracket syntax that confuses
me. A couple of examples from the fn in sanity.m4:

test "$[*]" != "X conftest.ts1 conftest.ts2" ||
..
test "$[]2" = conftest.ts3 &&
..
etc.

I've never seen anything like that before. Searching online, supposedly
$[...] means arithmetic expansion, but clearly that's not what is going
on here. I don't know what it means. Seems like just "$2" (for example)
is intended? I feel like I'm missing/forgetting something basic.

Sorry I didn't read the code when you submitted it originally :(.

Thanks,
Karl