use Benchmark qw( cmpthese );

my @input = ( 'x' x 100 ) x 1_000_000;

sub copy_array {
    my @copy = @{$_[0]};
    return @copy;
}
sub copy_grep {
    my @copy = grep /x/, @{$_[0]};
    return @copy;
}
sub return_grep {
    return grep /x/, @{$_[0]};
}
sub return_scalar_grep {
    return scalar grep /x/, @{$_[0]};
}
sub bare_grep        {        grep /x/, @{$_[0]} }
sub bare_scalar_grep { scalar grep /x/, @{$_[0]} }
sub bare_list_grep   { () =   grep /x/, @{$_[0]} }

cmpthese 100, { copy_array         => sub { copy_array(         \@input ) },
                copy_grep          => sub { copy_grep(          \@input ) },
                return_grep        => sub { return_grep(        \@input ) },
                return_scalar_grep => sub { return_scalar_grep( \@input ) },
                bare_grep          => sub { bare_grep(          \@input ) },
                bare_scalar_grep   => sub { bare_scalar_grep(   \@input ) },
                bare_list_grep     => sub { bare_list_grep(     \@input ) },
            };
__END__
                     Rate copy_grep copy_array bare_list_grep return_scalar_grep return_grep bare_scalar_grep bare_grep
copy_grep          1.23/s        --       -21%           -39%               -78%        -79%             -79%      -79%
copy_array         1.56/s       27%         --           -23%               -73%        -73%             -73%      -74%
bare_list_grep     2.02/s       65%        30%             --               -64%        -65%             -65%      -66%
return_scalar_grep 5.69/s      363%       265%           181%                 --         -2%              -2%       -4%
return_grep        5.78/s      371%       271%           185%                 2%          --              -1%       -3%
bare_scalar_grep   5.82/s      374%       274%           188%                 2%          1%               --       -2%
bare_grep          5.93/s      383%       280%           193%                 4%          3%               2%        --