Highly untested, but try this:

sub getPlatformFiles {
    my $plat_in = shift;
    my $nic = shift;
    my @list;
    if ($plat_in =~ /RedHat/) {
        @list = ("/etc-test/resolv.conf", 
                  "/etc-test/sysconfig/network-scripts/ifcfg-$nic->{de
+vice}");
    }
    return @list;
}
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You're passing in a list of two elements, so you need to shift the second one onto a more localized variable in order to access it within the subroutine.