$./025-6.pl -M1=keys -M2=pairs -N=1e6
hash built, starting timer
Took 3.931463 and 39.000MB extra memory for 1000000 using keys/pairs method
$./025-6.pl -M1=each -M2=pairs -N=1e6
hash built, starting timer
Took 2.434757 and 1.000MB extra memory for 1000000 using each/pairs method