Sorry - I tried returning \%filters first, but that didn't work. The code I posted is in a sub within a module, because I need to use it in several programs. Here's what I'm doing in the main program (when returning \%filters):

my($filters_ref) = GetFilters($filters_file);
%filters = %$filters_ref;

print \%filters;
foreach (keys %filters) { print; }
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I get a hash reference with the first print line but nothing with the second. I've tested the data in the hash and it's perfectly correct before I return it.