Change some strBEGINs() to memBEGINs()

The latter is generally faster when the length is already known.

This commit also changes a few hard-coded numbers to use sizeof().

1 files changed, 1 insertions, 1 deletions

diff --git a/pp_pack.c b/pp_pack.c
index f2d56b45f6..7033649475 100644
--- a/pp_pack.c
+++ b/pp_pack.c
@@ -191,7 +191,7 @@ S_mul128(pTHX_ SV *sv, U8 m)
 
   PERL_ARGS_ASSERT_MUL128;
 
-  if (! strBEGINs(s, "0000")) {  /* need to grow sv */
+  if (! memBEGINs(s, len, "0000")) {  /* need to grow sv */
     SV * const tmpNew = newSVpvs("0000000000");
 
     sv_catsv(tmpNew, sv);