I changed shell script like this. 
perl 025-1.pl each 10000 >  log
sleep 10;
perl 025-1.pl keys 10000 >> log
sleep 10;
perl 025-1.pl each 100000 >> log
sleep 10;
perl 025-1.pl keys 100000 >>  log
sleep 10;
perl 025-1.pl each 1000000 >> log
sleep 10;
perl 025-1.pl keys 1000000 >> log
sleep 10;
perl 025-1.pl each 2000000 >> log
sleep 10;
perl 025-1.pl keys 2000000 >> log

[download]
And result seems to show me "each" is slower than "keys", especially when hash becomes larger. 
###count=10000,each###
before    : size=8708096
after hash: size=11853824
after loop: size=11853824
time=0.051
###count=10000,keys###
before    : size=8708096
after hash: size=11853824
after loop: size=11853824
time=0.043
###count=100000,each###
before    : size=8708096
after hash: size=41213952
after loop: size=41213952
time=0.791
###count=100000,keys###
before    : size=8708096
after hash: size=41213952
after loop: size=41213952
time=0.680
###count=1000000,each###
before    : size=8708096
after hash: size=294969344
after loop: size=296017920
time=8.561
###count=1000000,keys###
before    : size=8708096
after hash: size=294969344
after loop: size=296017920
time=7.429
###count=2000000,each###
before    : size=8708096
after hash: size=581230592
after loop: size=582279168
time=309.887
###count=2000000,keys###
before    : size=8708096
after hash: size=581230592
after loop: size=582279168
time=99.701

[download]

My question is
1. Why Gtop says while loop and foreach loop consume exact same memory?
2. Why foreach/keys loop faster in this example? As another person kindly pointed me, Benchmark shows while/each loop is faster.

updated I didn't understand the output of Benchmark... Benchmark also says foreach/keys loop is faster. But question remains. Why?

In reply to Re^8: Finding the size of a nested hash in a HoH by remiah
in thread Finding the size of a nested hash in a HoH by Jeri

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