Well, I can't speak for Paul Graham, but I think that many of the special global variables are stunningly bad, especially all those that relate to filehandles. Either form of select is a botch. It turned out to be a bad idea to overload $, @, and % as context selectors for the subscript.

Basically, look at the Apocalypses from the viewpoint of figuring out what the p5-to-p6 translator will have to deal with, and that's where the stunningly bad bits tend to be.