I’d be willing to use the implicit global where the specific technical benefits of the iterator+block approach helps code clarity and maintainability in other ways, though — of course.

I agree about the obscurely named global variables — but I still prefer the ‘each’ form only because it uses a code block, so the block has its own local scope — any variables introduced therein will not persist thereafter. It’s more functional vs. imperative. Admittedly more about style than substance.

I also find the gets formulation a bit more readable, since it avoids the use of a cryptic global variable. Couple that with the probably more scalable resource management of it, and I still think I’d prefer the while line = gets version. If you have some good counterarguments, I’d love to see them.

Have you considered using a while gets loop for handling input for filter-type programs? It’s the Ruby equivalent to Perl’s while (here’s hoping that formats correctly):

while lines = gets
# do stuff
end

That way, it automagically takes filenames as arguments (once you’ve parsed everything else out of ARGV), takes input piped to it, or opens an interactive STDIN filehandle, depending on what you do with the command and its arguments. It’s pretty handy.