I'm wondering what other ways might you (better) obtain the number of days since monday (and friday for that matter) of the previous week?

use Time::ParseDate;
[download]

I'm not familiar with Time::ParseDate but at first sight it wouldn't seem the best tool to accomplish your task since your logic is much like "do, then undo". I suppose that some of the functions from Date::Calc (which I have advantageously used) may be better suited for it. Just a resonable guess...