From Rainer Weikusat@21:1/5 to All on Wed Nov 4 19:20:21 2020
\%by_addr = $$self[BY_ADDR] //= {};
This will (with refaliasing enabled) cause %by_addr to refer to the
anonymous hash stored in $$self[BY_ADDR]. If $$self[BY_ADDR] is
undefined, it'll first create an anonymous hash and assign a reference
to that to $$self[BY_ADDR].