val any : char tany, unlike "." by default, matches newline.
(However, note that of_re2 (Re2.create_exn ".") will match newline. See the comment on of_re2 for more information.)
val one_of : char list -> char tDuplicates in the lists given to one_of and not_one_of are ignored.
val not_one_of : char list -> char tval upper : char tA character matching Char.is_uppercase
val lower : char tA character matching Char.is_lowercase
val alpha : char tA character matching Char.is_alpha
val digit : char tA character matching Char.is_digit
val alnum : char tA character matching Char.is_alphanum
val space : char tA character matching Char.is_whitespace