Glad you like my little POD trick. I don't know of any automated modules for this - interesting idea!

I'm still unsure about the col 1 and col 2 stuff. I guess I keyed in on this phrase "(sorted based on second column..." and thought that was the primary key. My brain had a bit of trouble interpreting the spec. The test data doesn't have enough cases to unambiguously demonstrate the desired behavior. I hope the code is clear enough that the OP can make these precedence tweaks or other desired changes.

cheers, Marshall