#!/usr/bin/perl

use strict;
use warnings;
use Benchmark qw(cmpthese);

our @foo = 1 .. 10;

sub a {
    my @list = @{shift()};
    $_ += 1 foreach @list;
    return \@list;
}

sub b {
    my @list = @{shift()};
    return [map {$_ += 1} @list];
}

cmpthese(500_000, {
    a => sub {a(\@foo)},
    b => sub {b(\@foo)},
    c => 'my @list = @foo; $_ += 1 foreach @list; \@list',
    d => 'my @list = @foo; [map {$_ += 1} @list]',
});

__END__

      Rate    b    d    a    c
b  68587/s   --  -9% -39% -52%
d  74963/s   9%   -- -33% -48%
a 111607/s  63%  49%   -- -22%
c 143678/s 109%  92%  29%   --