In addition to the helpful advice already given, a handy debugging tool is Data::Dumper. This can help to get an idea of your array/hash contents at arbitrary points in your code: 
print Dumper(\%harry);

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It is also customary to post (small) segments of your data structures here to help us help you.

In reply to Re: Accessing (deleting) array elements in a hash of arrays by toolic
in thread Accessing (deleting) array elements in a hash of arrays by onslaught

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