I'll believe that when I see test code to demonstrate it. My recollection is that eof reads ahead to see whether you are at EOF rather than just returning whether Perl already knew that you were at EOF.

I can see eof allowing code to run just before an implicit close / open, but I'd be surprised to find eof not causing an implicit read() after it caused an implicit open().

Sorry, I'm not in a position to test it myself at the moment.