^Z
Benchmark: timing 1000000 iterations of regex1, regex2, substr...
    regex1:  4 wallclock secs ( 4.00 usr + -0.02 sys =  3.98 CPU) @ 251004.02/s (n=1000000)
    regex2:  3 wallclock secs ( 3.19 usr +  0.00 sys =  3.19 CPU) @ 313774.71/s (n=1000000)
    substr:  0 wallclock secs ( 0.72 usr +  0.00 sys =  0.72 CPU) @ 1390820.58/s (n=1000000)