Just set $delim to whatever character or sequence of characters is not going to be found inside any of your nested array fields. I used tabs.

use strict;
use warnings;
use Data::Dumper;

my @AoA = (['a','b','c'],
           ['a','b','c'],
           ['a','b','d'],
           ['a','b','d']);

my (%h, @uAoA);
for (@AoA) { push @uAoA, $_ if !$h{join $;, @$_}++; }

print Dumper \@uAoA;
[download]

EDIT: Edited code to use $;, as per suggestion.