'ROBO' => sub {
            my $i = @array;
            do {
                ++$cRO;
                my $j = int rand $i;
                @array[$i,$j] = @array[$j,$i];
            } while ($i--);
        },

roboticus@sparky:~$ perl 1088227.pl 
Benchmark: timing 500 iterations of BRANCH, IFIDDLE, ROBO, WITHOUT...
    BRANCH: 17 wallclock secs (17.05 usr +  0.00 sys = 17.05 CPU) @ 29.33/s (n=500)
   IFIDDLE: 14 wallclock secs (14.29 usr +  0.00 sys = 14.29 CPU) @ 34.99/s (n=500)
      ROBO: 19 wallclock secs (18.59 usr +  0.00 sys = 18.59 CPU) @ 26.90/s (n=500)
   WITHOUT: 15 wallclock secs (15.69 usr +  0.00 sys = 15.69 CPU) @ 31.87/s (n=500)
5000000, 5250000, 5000000, 5125250