Well, a quick read on how to interpret Devel::Peek info suggests that the output here explains why I was confused : the original value is not what it seemed it was, despite a variety of debug output to the contrary.

I also (think) I see why the unpack() + pack() pair of calls have the 'magical' effect that they are having.

The main thing for me is that this is no longer a mystery. I can see clearly how to work with the data, and why it is necessary. And, I learned something new.

Thanks again for the "finger pointing at the Moon".