The variant is from how List::Util Util.xs does it.
p4raw-id: //depot/perl@18826
# ifndef __PATCHLEVEL_H_INCLUDED__
# include <patchlevel.h>
# endif
-# ifndef PERL_VERSION
+# if !(defined(PERL_VERSION) || (SUBVERSION > 0 && defined(PATCHLEVEL)))
# include <could_not_find_Perl_patchlevel.h>
# endif
# ifndef PERL_REVISION