OOD as a teaching tool

OK I made a version of tmux 2.7 and was able to replicate this issue. Apparently it doesn’t like that field seperator and instead prints underscores. So even though we say one thing, it prints another and therefore can’t parse it. I’m submitting a patch shortly, but you should be able to edit this line and use a comma instead. I need to sort out what will be more reliable, but I don’t believe offhand bash (or any other shell) interprets commas as anything important.