const regexp/syntax.UnicodeGroups

3 uses

	regexp/syntax (current package)
		parse.go#L63: 	UnicodeGroups                   // allow \p{Han}, \P{Han} for Unicode group and negation
		parse.go#L69: 	Perl        = ClassNL | OneLine | PerlX | UnicodeGroups // as close to Perl as possible
		parse.go#L1516: 	if p.flags&UnicodeGroups == 0 || len(s) < 2 || s[0] != '\\' || s[1] != 'p' && s[1] != 'P' {