*_ is the symbol table entry (glob) containing $_ (and @_, %_, etc). Using local on globs is safer than using local on scalars.

I don't know why you are trying* to prove that read can do something <> can't. I didn't say you shouldn't use read. I didn't say it was useless. I didn't say <> can do everything read can.

* — You haven't come up with something yet. Keep in mind that length($buff) also returns the number of bytes read.