Benchmark: timing 1000000 iterations of map_browseruk,
 map_browseruk_setup, map_jwkrahn, map_jwkrahn_setup, unpack,
 unpack_setup...
map_browseruk: 16 wallclock secs (14.77 usr + 0.04 sys = 14.81 CPU) 
@ 67521.94/s (n=1000000)
map_browseruk_setup:  9 wallclock secs ( 9.27 usr + 0.03 sys =  9.30 
CPU) @ 107526.88/s (n=1000000)
map_jwkrahn: 29 wallclock secs (23.17 usr + 0.04 sys = 23.21 CPU) @ 
43084.88/s (n=1000000)
map_jwkrahn_setup: 23 wallclock secs (20.23 usr + 0.03 sys = 20.26 
CPU) @ 49358.34/s (n=1000000)
    unpack:  4 wallclock secs ( 2.43 usr + 0.00 sys =  2.43 CPU) @ 
411522.63/s n=1000000)
unpack_setup:  1 wallclock secs ( 0.44 usr + 0.00 sys =  0.44 CPU) 
@ 2272727.27/s (n=1000000)