[texhax] Parameter _2p in makeindex style file.

[Karl Berry]

    I don't find this in the manual. Can someone point me to documentation 
    on the subject?

I have no idea, but I wouldn't be surprised if there is none.  The
makeindex documentation has essentially never been updated (as far as I
know) since it was first written decades ago.  I suggest looking at the
sources.

If you or anyone would like to look at it with an eye towards a
general overhaul and update for today's world, comparing it with the
current sources, etc., that would be great.

Thanks,
karl