Allow push/pop/keys/etc to act on references

All built-in functions that operate directly on array or hash
containers now also accept hard references to arrays or hashes:

  |----------------------------+---------------------------|
  | Traditional syntax         | Terse syntax              |
  |----------------------------+---------------------------|
  | push @$arrayref, @stuff    | push $arrayref, @stuff    |
  | unshift @$arrayref, @stuff | unshift $arrayref, @stuff |
  | pop @$arrayref             | pop $arrayref             |
  | shift @$arrayref           | shift $arrayref           |
  | splice @$arrayref, 0, 2    | splice $arrayref, 0, 2    |
  | keys %$hashref             | keys $hashref             |
  | keys @$arrayref            | keys $arrayref            |
  | values %$hashref           | values $hashref           |
  | values @$arrayref          | values $arrayref          |
  | ($k,$v) = each %$hashref   | ($k,$v) = each $hashref   |
  | ($k,$v) = each @$arrayref  | ($k,$v) = each $arrayref  |
  |----------------------------+---------------------------|

This allows these built-in functions to act on long dereferencing
chains or on the return value of subroutines without needing to wrap
them in C<@{}> or C<%{}>:

  push @{$obj->tags}, $new_tag;  # old way
  push $obj->tags,    $new_tag;  # new way

  for ( keys %{$hoh->{genres}{artists}} ) {...} # old way
  for ( keys $hoh->{genres}{artists}    ) {...} # new way

For C<push>, C<unshift> and C<splice>, the reference will auto-vivify
if it is not defined, just as if it were wrapped with C<@{}>.

Calling C<keys> or C<values> directly on a reference gives a
substantial performance improvement over explicit dereferencing.

For C<keys>, C<values>, C<each>, when overloaded dereferencing is
present, the overloaded dereference is used instead of dereferencing
the underlying reftype.  Warnings are issued about assumptions made in
the following three ambiguous cases:

  (a) If both %{} and @{} overloading exists, %{} is used
  (b) If %{} overloading exists on a blessed arrayref, %{} is used
  (c) If @{} overloading exists on a blessed hashref, @{} is used

1 files changed, 3 insertions, 2 deletions

diff --git a/doop.c b/doop.c
index 35efba69b3..550e6fb2b6 100644
--- a/doop.c
+++ b/doop.c
@@ -1436,8 +1436,9 @@ Perl_do_kv(pTHX)
     register HE *entry;
     const I32 gimme = GIMME_V;
     const I32 dokv =     (PL_op->op_type == OP_RV2HV || PL_op->op_type == OP_PADHV);
-    const I32 dokeys =   dokv || (PL_op->op_type == OP_KEYS);
-    const I32 dovalues = dokv || (PL_op->op_type == OP_VALUES);
+    /* op_type is OP_RKEYS/OP_RVALUES if pp_rkeys delegated to here */
+    const I32 dokeys =   dokv || (PL_op->op_type == OP_KEYS || PL_op->op_type == OP_RKEYS);
+    const I32 dovalues = dokv || (PL_op->op_type == OP_VALUES || PL_op->op_type == OP_RVALUES);
 
     if (!hv) {
 	if (PL_op->op_flags & OPf_MOD || LVRET) {	/* lvalue */