Use of uninitialized value in concatenation (.) or string

If I run ./bind-snmp-stats.pl -all I get the following error multiple times.

Use of uninitialized value in concatenation (.) or string at ./bind9-snmp-stats.pl line 342.

I am running Perl 5 version 24 running Debian 9.4

root@dns1:~/bind9# perl -v

This is perl 5, version 24, subversion 1 (v5.24.1) built for x86_64-linux-gnu-thread-multi (with 81 registered patches, see perl -V for more detail)

Perl may be copied only under the terms of either the Artistic License or the GNU General Public License, which may be found in the Perl 5 source kit.

Complete documentation for Perl, including FAQ lists, should be found on this system using "man perl" or "perldoc perl". If you have access to the Internet, point your browser at http://www.perl.org/, the Perl Home Page.

Now like 342 is this line

debug(0, "$OID_BASE.4.1.$type_nr.$i = ".$DOMAINS{$domain}{$view}{$type}."\n") if($CFG{'DEBUG'});

Looks like something is wrong with the script. why is it giving me that error multiple times.

FransUrbo / snmp-modules

Use of uninitialized value in concatenation (.) or string #3