$ perl bench_oh.pl 1   # memory efficient and fast
Tie::Hash::Indexed
store  : 0.858 secs.
delete : 1.544 secs.
elapse : 2.401 secs.

$ perl bench_oh.pl 2   # not memory efficient, but fast for pure-Perl impl.
MCE::Shared::Indhash
store  : 1.271 secs.
delete : 2.197 secs.
elapse : 3.468 secs.

$ perl bench_oh.pl 3   # memory efficient and fast for being pure-Perl
MCE::Shared::Ordhash
store  : 1.048 secs.
delete : 2.829 secs.
elapse : 3.877 secs.

$ perl bench_oh.pl 4   # memory efficient, but deletions taking longer
Hash::Ordered
store  : 1.076 secs.
delete : 4.037 secs.
elapse : 5.113 secs.