use strict;
use warnings;

use Benchmark ();

sub t_for_r {
    my ($url, $list) = @_;
    my @return;
    push(@return, "$url/$_\n") foreach @$list;
    return @return;
}

sub t_map_r {
    my ($url, $list) = @_;
    my @return = map { "$url/$_\n" } @$list;
    return @return;
}

sub t_map2_r {
    my ($url, $list) = @_;
    return map { "$url/$_\n" } @$list;
}

sub t_for_a {
    my $url = shift;
    my @return;
    push(@return, "$url/$_\n") foreach @_;
    return @return;
}

sub t_map_a {
    my $url = shift;
    my @return = map { "$url/$_\n" } @_;
    return @return;
}

sub t_map2_a {
    my $url = shift;
    return map { "$url/$_\n" } @_;
}

{
   my $url = 'http://www.domain.com/';
   my @list = qw(
      file0 file1 file2 file3 file4
      file5 file6 file7 file8 file9
   );

   Benchmark::cmpthese(-3, {
      t_for_r  => sub { $a = join('', t_for_r ($url, \@list)); },
      t_map_r  => sub { $a = join('', t_map_r ($url, \@list)); },
      t_map2_r => sub { $a = join('', t_map2_r($url, \@list)); },
      t_for_a  => sub { $a = join('', t_for_a ($url,  @list)); },
      t_map_a  => sub { $a = join('', t_map_a ($url,  @list)); },
      t_map2_a => sub { $a = join('', t_map2_a($url,  @list)); },
   });
}

__END__

            Rate  t_for_r  t_map_r  t_for_a  t_map_a t_map2_r t_map2_a
t_for_r  20641/s       --      -3%      -5%      -5%     -33%     -36%
t_map_r  21196/s       3%       --      -2%      -2%     -31%     -34%
t_for_a  21651/s       5%       2%       --      -0%     -29%     -33%
t_map_a  21684/s       5%       2%       0%       --     -29%     -32%
t_map2_r 30598/s      48%      44%      41%      41%       --      -5%
t_map2_a 32087/s      55%      51%      48%      48%       5%       --
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At least for small lists, t_for and t_map are the same, and t_map2 is much faster.

Passing by ref vs passing the array doesn't matter if you use @_ directly.