Definitely not wanting to take away from Corion's answer above as it is very important, but I did notice something while glancing at the code.

In the for line, you use {devices}, but in the subsequent assignment to $CFG, you use {device}.

foreach my $name (@{ $heap->{cfg}->{devices} }) {
    my $CFG = $heap->{cfg}->{device}->{$name}->{localfile};
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We won't know whether this is a typo or not unless you post some Data::Dumper output.