use Benchmark qw(cmpthese);

our $a1='a'x1e6;
our $b1=12345;
cmpthese -1,{
    und=>q[ sub{ my( undef, $x) = @_ }->( $a1, $b1 ) ],
    skp=>q[ sub{ my $x = $_[1]        }->( $a1, $b1 ) ],
    var=>q[ sub{ my( $unused, $x ) = @_;}->( $a1, $b1 ) ],
};
#output
        Rate      var      und      skp
var   66.3/s       --     -10%    -100%
und   73.5/s      11%       --    -100%
skp 945230/s 1424595% 1286780%       --