[
          {
            'readings' => [
                            {
                              'KNOWN1' => '3.28',
                              'KNOWN2' => '34',
                              'KNOWN3' => '-73',
                              ...
                            }
                          ],
            'FWTYPE' => 'XXX',
            'FWID' => '123'
          }
];


##</code><code>##

$json = decode_json($POST);

# Extract data from JSON
for my $report ( @{$json} ) {

        $DBID = $report->{DBID};
        $DISKSIZE = $report->{readings}[0]{DISKSIZE};
        $DISKUSED = $report->{readings}[0]{DISKUSED};
        $DISKFREE = $report->{readings}[0]{DISKFREE};
        ...
}

##</code><code>##

[
          {
            'readings' => [
                            {
                              'asddad' => '123',
                              'fsfsf' => 'abc',
                              'sdfsdfsfsf' => 'x1y',
                              ...
                            }
                          ],
            'FWTYPE' => 'XXX',
            'FWID' => '123'
          }
];