cmpthese -1, { 
    a => q[ 
        my @a = 1 .. 1e5;
        @a[ $_, $_+2 ] = @a[ $_+2, $_ ] for 0 .. $#a-2 
    ],
    b => q[ 
        my( @a, $t ) = 1 .. 1e5;
        $t = $a[ $_ ], $a[ $_ ] = $a[ $_+2 ], $a[ $_+2 ] = $t for 0 .. $#a-2
    ] 
};;
    Rate    a    b
a 9.65/s   -- -13%
b 11.1/s  15%   --