Benchmark: running regex1, regex2, each for at least 30 CPU seconds...
    regex1: 31 wallclock secs (31.31 usr +  0.00 sys = 31.31 CPU) @ 655.10/s (n=20508)
    regex2: 31 wallclock secs (30.84 usr +  0.00 sys = 30.84 CPU) @ 530.35/s (n=16358)