$type Damnitaddie.pl
use strict;
use warnings;
use Data::Dumper;

my @rows = ( [qw(a b c  d)], [qw(e f c  h)], [qw(i j k  l)], );

my %seen;
@rows = grep {
    my $x = $_->[2];
    if ( exists $seen{$x} ) {
        $seen{$x}++;
        0;
    }
    else {
        $seen{$x} = 0;
        $seen{$x}++;
        1;
    }
} @rows;

#@rows = do { my %seen; grep { !$seen{$_->[2]}++ } @rows };

print Dumper( \@rows );

$perl Damnitaddie.pl
$VAR1 = [
          [
            'a',
            'b',
            'c',
            'd'
          ],
          [
            'i',
            'j',
            'k',
            'l'
          ]
        ];