Benchmark: timing 20 iterations of grep_sort, sort_grep...
 grep_sort:  5 wallclock secs ( 4.70 usr +  0.02 sys =  4.72 CPU) @  4.24/s (n=20)
 sort_grep: 16 wallclock secs (15.56 usr +  0.03 sys = 15.59 CPU) @  1.28/s (n=20)