We teach binmode, for use when we expect the file to be binary. If there were a layer I could pass to binmode which turned off binary, or turned everything back to text processing (text/reset/default/native) which didn't require another module to do it, I'd be thrilled. Unfortunately this doesn't seem to be the case.
I don't mind teaching my students that File::Temp assumes that temporary files will be binary by default. I was just hoping that someone could show me the easy, portable way we could revert that. But it doesn't seem to exist in Perl 5.10 and below. Perhaps I'll get a patch into File::Temp for 5.10.1, or alternately have some luck getting a layer for binmode which turns off binary.
Unfortunately in-memory files isn't really what I was looking for. They're cool, but they don't really solve the problem I was having. I want to be able to write out a file to a temporary location, then when I know that it's been fully written, I want to move the file over an original atomically. This means that at no point can someone access that file and get invalid data. Old previously-valid data, sure, but never only partly-written data.