+#if !defined(PERL_OLD_COPY_ON_WRITE) && !defined(PERL_NEW_COPY_ON_WRITE) && !defined(PERL_NO_COW)
+# define PERL_NEW_COPY_ON_WRITE
+#endif
+
+#if defined(PERL_OLD_COPY_ON_WRITE) || defined(PERL_NEW_COPY_ON_WRITE)
+# if defined(PERL_OLD_COPY_ON_WRITE) && defined(PERL_NEW_COPY_ON_WRITE)
+# error PERL_OLD_COPY_ON_WRITE and PERL_NEW_COPY_ON_WRITE are exclusive
+# else
+# define PERL_ANY_COW
+# endif
+#endif
+