the data in the array variable is lost. I have tried using our @net_pnics

You haven't shown any code, but I suspect you're checking in the wrong namespace (i.e. not Net::).

In other words, either use fully-qualified names

package Net;

our @net_pnics;

sub fill_array {
    @net_pnics = qw(foo bar);
}
1;
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#!/usr/bin/perl -wl
use strict;

use Net;

Net::fill_array();

print "@Net::net_pnics";    # "foo bar"
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or use Exporter to export the variable into the namespace of the script Main_Input.pl.