+// <regex> in gcc is unusable in versions less than 4.9.0
+// see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53631
+// clang defines __GNUC__ but how do the versions match?
+#ifndef LYX_USE_STD_REGEX
+# if (__GNUC__ == 4 && __GNUC_MINOR__ >= 9) || __GNUC__ > 4 || defined(USE_LLVM_LIBCPP)
+# define LYX_USE_STD_REGEX