+/* Checks if o acts as an in-place operator on an array. oright points to the
+ * beginning of the right-hand side. Returns the left-hand side of the
+ * assignment if o acts in-place, or NULL otherwise. */
+
+STATIC OP *
+S_is_inplace_av(pTHX_ OP *o, OP *oright) {
+ OP *o2;
+ OP *oleft = NULL;
+
+ PERL_ARGS_ASSERT_IS_INPLACE_AV;
+
+ if (!oright ||
+ (oright->op_type != OP_RV2AV && oright->op_type != OP_PADAV)
+ || oright->op_next != o
+ || (oright->op_private & OPpLVAL_INTRO)
+ )
+ return NULL;
+
+ /* o2 follows the chain of op_nexts through the LHS of the
+ * assign (if any) to the aassign op itself */
+ o2 = o->op_next;
+ if (!o2 || o2->op_type != OP_NULL)
+ return NULL;
+ o2 = o2->op_next;
+ if (!o2 || o2->op_type != OP_PUSHMARK)
+ return NULL;
+ o2 = o2->op_next;
+ if (o2 && o2->op_type == OP_GV)
+ o2 = o2->op_next;
+ if (!o2
+ || (o2->op_type != OP_PADAV && o2->op_type != OP_RV2AV)
+ || (o2->op_private & OPpLVAL_INTRO)
+ )
+ return NULL;
+ oleft = o2;
+ o2 = o2->op_next;
+ if (!o2 || o2->op_type != OP_NULL)
+ return NULL;
+ o2 = o2->op_next;
+ if (!o2 || o2->op_type != OP_AASSIGN
+ || (o2->op_flags & OPf_WANT) != OPf_WANT_VOID)
+ return NULL;
+
+ /* check that the sort is the first arg on RHS of assign */
+
+ o2 = cUNOPx(o2)->op_first;
+ if (!o2 || o2->op_type != OP_NULL)
+ return NULL;
+ o2 = cUNOPx(o2)->op_first;
+ if (!o2 || o2->op_type != OP_PUSHMARK)
+ return NULL;
+ if (o2->op_sibling != o)
+ return NULL;
+
+ /* check the array is the same on both sides */
+ if (oleft->op_type == OP_RV2AV) {
+ if (oright->op_type != OP_RV2AV
+ || !cUNOPx(oright)->op_first
+ || cUNOPx(oright)->op_first->op_type != OP_GV
+ || cGVOPx_gv(cUNOPx(oleft)->op_first) !=
+ cGVOPx_gv(cUNOPx(oright)->op_first)
+ )
+ return NULL;
+ }
+ else if (oright->op_type != OP_PADAV
+ || oright->op_targ != oleft->op_targ
+ )
+ return NULL;
+
+ return oleft;
+}
+