Unfortunately, I can't really help here because I don't think what you showed here is very representative, and there are a couple of inconsistencies: for example, you say "my input array of 30k elements became an output of one undef entry" but later "At this point @output is empty ... This time I don't see 0 results", or your last piece of example code shows prints of strings that don't apppear in exactly the same way in the example output, which means this isn't exactly the code you ran. Please see Short, Self-Contained, Correct Example - something that we can run ourselves will be much more helpful to us and therefore to you. Also, you never show us what $machine_aref actually looks like (Data::Dump or Data::Dumper with $Data::Dumper::Useqq=1;), but that data structure is really central to your question.