Make keys $scalar an lvalue

This does a run-time check to see whether $scalar is a hash ref, and
dies if it is not.

This is to keep keys \@_ consistent with keys @_.

I cannot simply use OPf_MOD, since that indicates *potential* lvalue
context (including subroutine args).

So, instead, I take advantage of the fact that OPf_SPECIAL is always
set on the LHS of an assignment (usually to indicate that local()
should not erase the value).

1 files changed, 6 insertions, 0 deletions

diff --git a/pp.c b/pp.c
index 5b32daf78e..4c8827065a 100644
--- a/pp.c
+++ b/pp.c
@@ -4850,6 +4850,12 @@ PP(pp_rkeys)
 	    PL_op_desc[PL_op->op_type] );
     }
 
+    if (PL_op->op_flags & OPf_SPECIAL && SvTYPE(sv) == SVt_PVAV)
+	DIE(aTHX_
+	   "Can't modify %s in %s",
+	    PL_op_desc[PL_op->op_type], PL_op_desc[PL_op->op_next->op_type]
+	);
+
     /* Delegate to correct function for op type */
     PUSHs(sv);
     if (PL_op->op_type == OP_RKEYS || PL_op->op_type == OP_RVALUES) {