use Data::Dumper;

##</code><code>##

print Dumper(\%data), "\n";

##</code><code>##

while ( my ($nbname, $ip) = $sth->fetchrow ) {
if ($ip) {
  print "DB has IP=$ip for nbname=$nbname.\n";
} else {
  print "DB has no IP value for nbname=$nbname.\n";
    if ($data{$nbname}{'IP'}) {
      print "... but CSV file has value: $data{$nbname}{'IP'}.\n";
    }
  }
}