change 
%hash = (
             $unit_num => {
                $event_nm => [ $event_date ],
   },
  );

@HoH{keys %hash} = values %hash

[download]
to 
push @{$HoH{$unit_num}{$event_nm}}, $event_date;

[download]

In reply to Re: Using a hash to store complex data by Anonymous Monk
in thread Using a hash to store complex data by TJRandall

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