As stated in the previous change, conditional hash assignments
which trigger other hash assignments seem problematic, at times.
So replace:
$h->{k} //= do { $h->{x} = ...; $val };
$h->{k} // do {
$h->{x} = ...;
$hk->{k} = $val
};
"||=" is affected the same way, and some instances of "||=" are
replaced with "//=" or "// do {", now.