perl -we'
($m, $i) = @ARGV;
use Benchmark;
timethese($i, {
block   => sub { $x = 0; while (++$x < $m) { $x++ } },
noblock => sub { $x = 0; ++$x while ++$x < $m }
});' 100000 1000
Benchmark: timing 1000 iterations of block, noblock...
     block:  9 wallclock secs ( 9.10 usr +  0.00 sys =  9.10 CPU) @ 109.89/s (n=1000)
   noblock:  8 wallclock secs ( 8.07 usr +  0.00 sys =  8.07 CPU) @ 123.92/s (n=1000)