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