You should delete all elements of the array each time through the loop, not assign the value undef to the 1st element. Change: 
        @net_configs = undef;

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to: 
        @net_configs = ();

[download]

Tip #4 from the Basic debugging checklist: Data::Dumper

In reply to Re: Use of uninitialized value $_ in pattern match (m//) by toolic
in thread Use of uninitialized value $_ in pattern match (m//) by stroke

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