This is just a warning (seen because of '-w' command line option in perl) indicating $na_can_use_ipv6 is used before initialization.
This is not going to affect the functionality. So, you can ignore the warning.
If the warnings are preventing you from execution, then don't use the '-w' option for the time being (as a workaround).
Meanwhile, we will see if we can fix all the warnings in the upcoming releases of NMSDK.