perl bin/algorithm3.pl 1_000_000_000
Prime numbers : 50847534
Compute time  : 0.163 sec

perl bin/primesieve.pl 1_000_000_000
Prime numbers : 50847534
Compute time  : 0.071 sec

perl bin/primeutil.pl 1_000_000_000
Prime numbers : 50847534
Compute time  : 0.025 sec

perl -Mntheory=:all -E 'say prime_count(1e9)'
50847534
0.020s user time