use strict;
use warnings;

my %seen;
my @array = (["1", "1", "3"], ["1", "5", "6"], ["1", "1", "3"]);
my @unique = grep {! $seen{$_->[1]}++} @array;

print "@$_\n" for @array;
print "\n";

map {$_++} @$_ for @unique;

print "@$_\n" for @array;
print "\n";

##</code><code>##

1 1 3
1 5 6
1 1 3

2 2 4
2 6 7
1 1 3

##</code><code>##

use strict;
use warnings;

my %seen;
my @array = (["1", "1", "3"], ["1", "5", "6"], ["1", "1", "3"]);
my @unique = map {[@$_]} grep {! $seen{$_->[1]}++} @array;

print "@$_\n" for @array;
print "\n";

map {$_++} @$_ for @unique;

print "@$_\n" for @array;
print "\n";
print "@$_\n" for @unique;
print "\n";

##</code><code>##

1 1 3
1 5 6
1 1 3

1 1 3
1 5 6
1 1 3

2 2 4
2 6 7