+# there *may* be common scalar items on both sides of a list assign:
+# run-time checking will be needed.
+addbits('aassign', 6 => qw(OPpASSIGN_COMMON_SCALAR COM_SCALAR));
+#
+# as above, but it's possible to check for non-commonality with just
+# a SvREFCNT(lhs) == 1 test for each lhs element
+addbits('aassign', 5 => qw(OPpASSIGN_COMMON_RC1 COM_RC1));
+
+# run-time checking is required for an aggregate on the LHS
+addbits('aassign', 4 => qw(OPpASSIGN_COMMON_AGG COM_AGG));