How do I find if an array has duplicate elements, if so discard it?

toddprof has asked for the wisdom of the Perl Monks concerning the following question: ⭐ (arrays)

@A = (1, 2, 3, 4, 5) ;
@B = (6, 7, 7, 8, 9) ;
@C = (10, 11, 12, 13, 15) ;

@D = ( @A , @B , @C );
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Since @B has duplicates (7,7) It should not appear in @D. In the end @D should contain only sets @A and @C

Originally posted as a Categorized Question.