\w Matches an alphanumeric character. Alphanumeric includes '_'.
\W Matches a nonalphanumeric character.
\s Matches a whitespace character. This includes spaces and tabs.
\S Matches a nonwhitespace character.
\d Matches a digit.
\D Matches a nondigit character.
\b Matches a word boundary.
\B Matches a nonword boundary.
\A Matches only at beginning of string.
\Z Matches only at end of string.
\G Matches only where previous m//g left off.