use Data::Dumper;
my %uniq;
my @aoa = ( ['foo',0],  # Changed from 'AoA' to 'aoa'. Thanks to bobf.
            ['foo',1],
            ['foo',2],
            ['foo',3],
            ['foo',4], 
            ['foo',5],);

@uniq{ @aoa[ 1 ... $#aoa ]->[-1] } = ();
print Dumper \%uniq;