Make C<undef ~~ 0> and C<undef ~~ ""> not match (like in 5.10.0)

This makes ~~ commutative with regard to undef, and fixes an
inconsistency, since C<undef ~~ [0]> was not matching, and ~~
should be distributive in this case.

1 files changed, 4 insertions, 0 deletions

diff --git a/pp_ctl.c b/pp_ctl.c
index 6bb5b40e5e..59ac8c12a8 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -4393,6 +4393,10 @@ S_do_smartmatch(pTHX_ HV *seen_this, HV *seen_other)
 	SP -= 2;
 	goto sm_any_scalar;
     }
+    else if (!SvOK(d)) {
+	/* undef ~~ scalar ; we already know that the scalar is SvOK */
+	RETPUSHNO;
+    }
     else
   sm_any_scalar:
     if (SvNIOK(e) || (SvPOK(e) && looks_like_number(e) && SvNIOK(d))) {