The eventual solution found by sapnac got buried below so I'll re-mention it here with an explanation. The issue is in the "initialization" code

 our @arrayAoH = "";
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The problem is that this doesn't just create an array. It creates an array with a single element that contains an empty string. It's basically equivalent to

our @arrayAoH;
$arrayAoH[0] = "";
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The solution is to either leave out the assignment or to assign it an empty list (which is different from an empty string):

our @arrayAoH = ();
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More formally, a simple scalar value in list context is treated as a list of length one containing that value.