$ /opt/cperl-5.24.3c/bin/cperl -I. tbench1.pl x.tmp 2   # pack i2
cell count at start = 1500000
run benchmark for 2 ticks
cell count at end = 1500000
time taken: 37 secs

$ /opt/cperl-5.24.3c/bin/cperl -I. tbench1.pl x.tmp 2   # mapping
cell count at start = 1500000
run benchmark for 2 ticks
cell count at end = 1500000
time taken: 38 secs