Obviously, if you use longer keys, perl requires more memory to store them. Here's a simple program that creates a hash with given key length and shows how much memory it uses, so you can see how it depends:

use strict;
use warnings;
use Devel::Size qw(total_size);

my $length = $ARGV[0];

my $key = "a" x $length;
my %hash;

for ( 1 .. 1_000_000 ) {
    $hash{$key} = 1;
    $key++;
}

print "key size: $length\n";
print `ps -p $$ v`;
print total_size( \%hash ), "\n";

__END__
key size: 8
  PID TTY      STAT   TIME  MAJFL   TRS   DRS   RSS %MEM COMMAND
22551 pts/0    S+     0:01      0     3 146484 128864  3.1 perl hash_k
+eys.pl 8
74388680
key size: 16
  PID TTY      STAT   TIME  MAJFL   TRS   DRS   RSS %MEM COMMAND
22557 pts/0    R+     0:01      0     3 146484 128860  3.1 perl hash_k
+eys.pl 16
82388680
key size: 32
  PID TTY      STAT   TIME  MAJFL   TRS   DRS   RSS %MEM COMMAND
22563 pts/0    R+     0:01      0     3 162116 144488  3.5 perl hash_k
+eys.pl 32
98388680
key size: 64
  PID TTY      STAT   TIME  MAJFL   TRS   DRS   RSS %MEM COMMAND
22569 pts/0    S+     0:01      0     3 193384 175740  4.3 perl hash_k
+eys.pl 64
130388680
key size: 128
  PID TTY      STAT   TIME  MAJFL   TRS   DRS   RSS %MEM COMMAND
22575 pts/0    R+     0:01      0     3 255936 238240  5.8 perl hash_k
+eys.pl 128
194388680
key size: 256
  PID TTY      STAT   TIME  MAJFL   TRS   DRS   RSS %MEM COMMAND
22581 pts/0    R+     0:02      0     3 380928 363244  8.9 perl hash_k
+eys.pl 256
322388680
key size: 512
  PID TTY      STAT   TIME  MAJFL   TRS   DRS   RSS %MEM COMMAND
22587 pts/0    S+     0:04      0     3 630924 613252 15.1 perl hash_k
+eys.pl 512
578388680
key size: 1024
  PID TTY      STAT   TIME  MAJFL   TRS   DRS   RSS %MEM COMMAND
22597 pts/0    R+     0:07      0     3 1130868 1113256 27.4 perl hash
+_keys.pl 1024
1090388680

[download]

In reply to Re: strange keys with a hash by zwon
in thread strange keys with a hash by chuckd

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.