# If record 'd' does not exist,
# if record 'd' exists but has no field 'value',
# if record 'd' exists and has field 'value' but is undefined,
# if record 'd' exists and has field 'value' but is 0,
# if record 'd' exists and has field 'value' but is "0", or
# if record 'd' exists and has field 'value' but is '':
if (!$hash{'d'} || !$hash{'d'}{'value'})