Index: clang/include/clang/Frontend/VerifyDiagnosticConsumer.h
===================================================================
--- clang/include/clang/Frontend/VerifyDiagnosticConsumer.h
+++ clang/include/clang/Frontend/VerifyDiagnosticConsumer.h
@@ -157,7 +157,8 @@
 /// In this example, the diagnostic may appear only once, if at all.
 ///
 /// Regex matching mode may be selected by appending '-re' to type and
-/// including regexes wrapped in double curly braces in the directive, such as:
+/// including regexes (using POSIX extended regular expression syntax) wrapped
+/// in double curly braces in the directive, such as:
 ///
 /// \code
 ///   expected-error-re {{format specifies type 'wchar_t **' (aka '{{.+}}')}}