> perl list_util.pl 1000 1   
Benchmark: running Grep, Util for at least 1 CPU seconds...
      Grep:  1 wallclock secs ( 1.06 usr +  0.00 sys =  1.06 CPU) @ 4830.19/s (n=5120)
      Util:  1 wallclock secs ( 0.94 usr +  0.14 sys =  1.08 CPU) @ 176987.04/s (n=191146)
> perl list_util.pl 1000 500
Benchmark: running Grep, Util for at least 1 CPU seconds...
      Grep:  1 wallclock secs ( 1.07 usr +  0.00 sys =  1.07 CPU) @ 4785.05/s (n=5120)
      Util:  1 wallclock secs ( 1.05 usr +  0.01 sys =  1.06 CPU) @ 11269.81/s (n=11946)
> perl list_util.pl 1000 1000
Benchmark: running Grep, Util for at least 1 CPU seconds...
      Grep:  1 wallclock secs ( 1.06 usr +  0.00 sys =  1.06 CPU) @ 4830.19/s (n=5120)
      Util:  1 wallclock secs ( 1.06 usr +  0.01 sys =  1.07 CPU) @ 5910.28/s (n=6324)
> perl list_util.pl 1000 1001
Benchmark: running Grep, Util for at least 1 CPU seconds...
      Grep:  1 wallclock secs ( 1.12 usr +  0.00 sys =  1.12 CPU) @ 4799.11/s (n=5375)
      Util:  2 wallclock secs ( 1.07 usr +  0.01 sys =  1.08 CPU) @ 5855.56/s (n=6324)