Thanks for the benchmark! (Same thanks goes to Tux and BrowserUk).

Hmm. This is what I got. I changed to using subs instead:

use Benchmark qw(cmpthese);

my $a1='a'x9999999;
my $b1=12345;
cmpthese -1,{
    und=> sub { sub{ my( undef, $x) = @_ }->( $a1, $b1 ) },
    skp=> sub { sub{ my $x = $_[1]        }->( $a1, $b1 ) },
    var=> sub { sub{ my( $unused, $x ) = @_;}->( $a1, $b1 ) },
};

__END__
        Rate      var      und      skp
var   50.2/s       --    -100%    -100%
und 516222/s 1027915%       --     -32%
skp 762291/s 1517942%      48%       --
[download]