But I see, that within square brackets the dot must be escaped.

Yes, you've got the idea its just the lingo you need help with now :) escaping means prefixing it with a backslash -- ie turn "." into "\." but that isn't required, as inside a character class [.] the dot is not a metacharacter, it is a literal character

(?s:.) means any character (including \n) alias [\w\W] alias [\s\S] alias [\d\D] alias \p{All}