Benchmark: timing 100000000 iterations of double_grep, grep_and, lookahead_grep...

double_grep	:
27 wallclock secs (26.98 usr +  0.00 sys = 26.98 CPU) @ 3705899.79/s (n=100000000)

grep_and	:
24 wallclock secs (23.05 usr +  0.00 sys = 23.05 CPU) @ 4338959.52/s (n=100000000)

lookahead_grep	:
24 wallclock secs (22.83 usr +  0.00 sys = 22.83 CPU) @ 4380585.25/s (n=100000000)