His bad formatting mislead you. He wants to turn

@AoD = ([11,12,22], [11,12,22], [13,15,18]);
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into

@AoD = ([11,12,22], [13,15,18]);
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Ignoring that, the advantage of previously mentioned

my %seen
@AoD = grep !$seen{$_}++, @AoD;
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over your solution

my %seen = map { $_ => 1 } @AoD;
@AoD = keys(%seen);
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is that the former maintains the order of the elements it keeps.