definetly pass $yesterday to avoid demerphq's unintended global

Well, if you have subs at the bottom and main code outside of a block, like this author has, ALL lexicals that aren't in a block, are semi-global. So you can avoid having this one as an "inintended global" by putting it in the if-block, but that still leaves all unblocked lexicals. In this stripped piece of code, that's only $today, but in larger programs the results can be disastrous.

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