simplify keys(%tied_hash) in boolean context.

Previously something like

    if (keys %tied_hash) { ... }

would have called FIRSTKEY(), followed by NEXTKEY() x N.

Now, it just calls SCALAR() once if present, and if not, falls
back to calling just FIRSTKEY() once.

i.e. it only needs to determine whether at least one key is present.

The behaviour of of 'keys(%tied) in boolean context now matches that of
'(%tied) in boolean context.

See http://nntp.perl.org/group/perl.perl5.porters/245463.

1 files changed, 6 insertions, 3 deletions

diff --git a/pp_hot.c b/pp_hot.c
index e2d9608ad8..a44ee34d9e 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -993,9 +993,12 @@ S_padhv_rv2hv_common(pTHX_ HV *hv, U8 gimme, bool is_keys, bool has_targ)
 	  || (  PL_op->op_private & OPpMAYBE_TRUEBOOL
 	     && block_gimme() == G_VOID)
           )
-	  && !tied
-    )
-	PUSHs(HvUSEDKEYS(hv) ? &PL_sv_yes : &PL_sv_zero);
+    ) {
+        if (tied)
+            PUSHs(Perl_hv_scalar(aTHX_ hv));
+        else
+            PUSHs(HvUSEDKEYS(hv) ? &PL_sv_yes : &PL_sv_zero);
+    }
     else if (gimme == G_SCALAR) {
         if (is_keys) {
             IV i;