14.5.1.3 The Match-not-syntactic-class Operator (\Sclass)

This operator is similar to the match-syntactic-class operator except that it matches any character whose syntactic class is not represented by the specified character. ‘\Sclass’ represents this operator. For example, ‘w’ represents the syntactic class of word-constituent characters, so ‘\Sw’ matches any character that is not word-constituent.