Don’t use [A-Z], that’s a red flag. It only works for English, at most.

There is a lot of software that only works for Englsh; I'm not sure I'd call it a "red flag". Maybe more flexibility should be used in this case, and maybe it doesn't matter. Don't get me wrong... it's good advice. I just don't see a "red flag" when I see [A-Z] unless I know that the program needs to deal with character sets other than ASCII. That has been rare in my world (though decreasingly so.)

-sauoq
"My two cents aren't worth a dime.";