p4raw-id: //depot/perl@25341
(last->op_private & OPpCONST_STRICT) &&
(oa = first->op_sibling) && /* The fh. */
(oa = oa->op_sibling) && /* The mode. */
+ (oa->op_type == OP_CONST) &&
SvPOK(((SVOP*)oa)->op_sv) &&
(mode = SvPVX_const(((SVOP*)oa)->op_sv)) &&
mode[0] == '>' && mode[1] == '&' && /* A dup open. */