This is likely a good case to comment since when debugging having a reminder that defined false values may be overwritten.

You're perfectly right. But, if one is aware of what he is doing ||= does its job most of the time. Of course we all will welcome //= to cover the remaining cases.

Occasionally I use ||= on purpose to overwrite a false value (with another "standardized" false value), e.g.:

$u ||= '';
# or
$v ||= 0;
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(Most often this is not necessary either, and -as usual- there are other ways to do it...)