$ perl a.pl
Benchmark: timing 100 iterations of for_each, for_loop, while_pop, while_shift...
  for_each:  4 wallclock secs ( 3.85 usr +  0.01 sys =  3.86 CPU) @ 25.91/s (n=100)
  for_loop:  7 wallclock secs ( 7.36 usr +  0.01 sys =  7.37 CPU) @ 13.57/s (n=100)
 while_pop:  5 wallclock secs ( 5.35 usr +  0.00 sys =  5.35 CPU) @ 18.69/s (n=100)
while_shift:  5 wallclock secs ( 5.38 usr +  0.00 sys =  5.38 CPU) @ 18.59/s (n=100)