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        'ROBO' => sub {
            my $i = @array;
...
      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

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

roboticus@sparky:~$ perl 1088227.pl 
Benchmark: timing 500 iterations of BRANCH, IFIDDLE, ROBO, WITHOUT...
...
      ROBO:  8 wallclock secs ( 7.85 usr +  0.00 sys =  7.85 CPU) @ 63
+.69/s (n=500)
   WITHOUT: 15 wallclock secs (15.33 usr +  0.00 sys = 15.33 CPU) @ 32
+.62/s (n=500)
roboticus@sparky:~$