Description: fix failure under perl 5.26
 Ever since perl’s lvalue subs were introduced, perl itself has been
 checking the OPf_MOD flag on the entersub op, not the OPf_REF flag, which
 was ignored. I needed an extra flag on entersub to fix a bug (the private
 flags are full), so I thought the OPf_REF flag was free game. I do think it
 is appropriate for this module to check the same flag for lvalue context
 that perl itself has been checking all this time.
Origin: CPAN RT #117618
Bug: https://rt.cpan.org/Public/Bug/Display.html?id=117618
Forwarded: https://rt.cpan.org/Public/Bug/Display.html?id=117618
Author: Father Chrysostomos <sprout@cpan.org>
Last-Update: 2017-06-19

--- a/Swap.xs
+++ b/Swap.xs
@@ -135,7 +135,7 @@
 	I32 sref;
 	SV *sv;
     PPCODE:
-	sref = (GIMME == G_SCALAR) && (PL_op->op_flags & OPf_REF);
+	sref = (GIMME == G_SCALAR) && (PL_op->op_flags & OPf_MOD);
 	for (i = 0; i < items; i++) {
 		if (!SvROK(ST(i))) {
 			STRLEN z;