Found an error immediately "Any lowercase character" doesn't match all Swedish lowercase characters.
lol really? Why not? Is that true for all encodings? Is it a bug or a feature? What about a simple character set like gsm-7 Swedish?
The author says “any lowercase character” but they mean “any character between the character ‘a’ and the character ‘z’”, which happens to correspond to the lower case letters in English but doesn’t include ü, õ, ø, etc.
I would expect [a-z] to mean any lowercase in any language, not lowercase but only a to z. So I’d get bitten by that one.