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use Data::Dumper;
...
    map { $h{$_}++ == 0 ? $_ : () } @_;
    print Dumper \%h;
}

$VAR1 = {
          'ARRAY(0x224ff8)' => 1,
...
          'ARRAY(0x1875904)' => 1,
          'ARRAY(0x224ef0)' => 1
        };

use Data::Dumper;
use List::MoreUtils qw(uniq);
...
my @AoA = ($a, $a, $b, $b);
my @uAoA = uniq(@AoA);
print Dumper(\@uAoA);