FWIW (after a few runs, this seems representative; too impatient to do higher iterations):

#!/usr/bin/perl
use strict;
use warnings;
use Benchmark ":all";
my $len = 1_000;
sub returnlist { my @rray = map({rand()} (1..$len)); return( @rray); }
sub returnref  { my @rray = map({rand()} (1..$len)); return(\@rray); }
cmpthese(10_000, {
    "returnlist" => sub { my  @foo = returnlist(); },
    "returnref"  => sub { my ($foo) = returnref(); },
});
__END__
            Rate returnlist  returnref
returnlist 633/s         --       -24%
returnref  829/s        31%         --
[download]

# perl -v
This is perl, v5.10.1 (*) built for i686-cygwin-thread-multi-64int

(Cygwin 1.7 on 32bit XP)