change sv_setsv(sv,NULL) to sv_set_undef(sv)

There are still a few core occurrences of

    sv_setsv(sv, NULL);

which is equivalent to

    sv_setsv(sv, &PL_sv_undef);

but which can now be done more efficiently with

    sv_set_undef(sv);

1 files changed, 1 insertions, 1 deletions

diff --git a/pp_hot.c b/pp_hot.c
index d4b32c9ff0..c580f26021 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -2245,7 +2245,7 @@ Perl_do_readline(pTHX)
 	if (gimme == G_SCALAR) {
 	    /* undef TARG, and push that undefined value */
 	    if (type != OP_RCATLINE) {
-		sv_setsv(TARG,NULL);
+		sv_set_undef(TARG);
 	    }
 	    PUSHTARG;
 	}