So you want sorting based on comparison of ITEM1, 2, and 3 in that order? Try:

@sorted = sort { $hash{$a}{ITEM1} <=> $hash{$b}{ITEM1} ||
                 $hash{$a}{ITEM2} <=> $hash{$b}{ITEM2} ||
                 $hash{$a}{ITEM3} <=> $hash{$b}{ITEM3} }
                 keys %hash;
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