Eventually, I decided I would not write code like that, fascinating as it is - it turns out to be just a way to avoid declaring a local variable. It works just as well replacing all instances of that and "$_'_" with "$Column_Index", and becomes a lot more readable ("local *_'_" being replaced by "my $Column_Index" helps by functioning without resorting to "no strict 'refs'").
I'm hoping this node helps other monks who may not have unraveled "_'_".
I'm also curious as to how this would be written in idiomatic perl6.
"As you get older three things happen. The first is your memory goes, and I can't remember the other two... " - Sir Norman Wisdom