Adding the "use open qw/:std :utf8/;" pragma did not remove the useless warning. It shouldn't, if I understand things correctly. That is because the source of the "wide characters" is embedded in the code itself, and is not brought in from an external file which must be opened. I am unaware of a way to encode the source code itself, or to decode it, save for the "use utf8;" pragma within the code itself. I have tested the code both with and without those characters in that HTML header, and removing them is the only way to erase the error message. I'm not willing to do that, because I want that heading. I suppose I should really just add a "no warnings;" to the code, the opposite of "use warnings;". That would silence the false alarm.
To be honest, in this day and age, having UTF8 characters in the code should be a complete non-issue. The "use utf8;" pragma should be unnecessary. It should be the built-in default. Ditto with the open pragma.
It may be worth noting that I have already required UTF8 for the HTML form, and have specified it in the output, i.e.:
<HTML lang="utf8">
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf8">