http://blogs.perl.org/users/byterock/2014/01/here-we-go-loop-de-loop.html#comment-1314935

test.pl

use strict;
use warnings;
use Benchmark;
use List::MoreUtils qw(minmax uniq part);
use Test::More tests => 1;

my @set; push @set, int(rand()*1000) for 1..10_000;
my $pivot_a = 333;
my $pivot_b = 666;

my %benchmarks = (
    'ListMoreUtils' => sub {
        my ($set_min, $set_max) = minmax @set;
        my @unique_set = uniq @set;
        my (undef,$sub_set_a) = part { $_ <= $pivot_a } @set;
        my (undef,$sub_set_b) = part { $_ > $pivot_a and $_<=$pivot_b } @set;
        my (undef,$sub_set_c) = part { $_ > $pivot_b } @set;
        return [$set_max, $set_min, \@unique_set, $sub_set_a, $sub_set_b, $sub_set_c];
    },
    'ForLoop' => sub {
        my ($set_min,$set_max,%unique,@sub_set_a,@sub_set_b,@sub_set_c);
        foreach my $item (@set){
            $set_max = $item if (! defined $set_max || $item > $set_max);
            $set_min = $item if (! defined $set_min || $item < $set_min);
            $unique{$item}=1;
            push(@sub_set_a,$item) if ($item <= $pivot_a);
            push(@sub_set_b,$item) if (($item > $pivot_a) and ($item <= $pivot_b));
            push(@sub_set_c,$item) if ($item > $pivot_b);
        }
        return [$set_max, $set_min, [keys %unique], \@sub_set_a, \@sub_set_b, \@sub_set_c];
    },
);

timethese(1_000, \%benchmarks);

use Data::Dumper qw( Dumper );
my $result_a = $benchmarks{'ListMoreUtils'}->();
my $result_b = $benchmarks{'ForLoop'}->();
for ($result_a,$result_b) {
    for my $ii (2,3,4,5) {
        $_->[$ii] = [sort {$a<=>$b} @{$_->[$ii]}];
    }
}
is_deeply( $result_a, $result_b, "Do they match");