Benchmark: timing 50 iterations of execute_each, using_in...
execute_each: 227 wallclock secs ( 6.73 usr +  1.41 sys =  8.14 CPU) @  6.14/s (n=50)
  using_in: 17 wallclock secs ( 1.39 usr +  0.08 sys =  1.47 CPU) @ 34.06/s (n=50)