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

my @arr = (
    [12, "abc", 30],
    [24, "abc", 30],
    [26, "abc", 30],
    [14, "abc", 40],
    [46, "abc", 40],
    [2,  "abc", 50]
);

my %res;

map { push @{$res{$_->[2]}}, $_ } @arr;

warn Dumper values %res;

##</code><code>##

$ perl tst.pl
$VAR1 = [
          [
            2,
            'abc',
            50
          ]
        ];
$VAR2 = [
          [
            14,
            'abc',
            40
          ],
          [
            46,
            'abc',
            40
          ]
        ];
$VAR3 = [
          [
            12,
            'abc',
            30
          ],
          [
            24,
            'abc',
            30
          ],
          [
            26,
            'abc',
            30
          ]
        ];