perl hash loop: keys() vs values()

[richard]

Hi

I'm trying to understand the difference between the keys() and values ()
operators. What I'm not getting is why a hash must be reversed to get the
key corresponding to a value? (as stated in perldoc). Can someone explain
this please?

Here is my test script; My perl is freebsd 5.8.9

use warnings;
use strict;

my %hds = ('1', '0C8CB35F', '2', '0C9CB37D');
print "rows: " . scalar keys(%hds) . "\n\n";

my $value;
my $key;

  foreach $value (values %hds) {
    print "key: $hds{$value} \n";
    print "value: $value \n";
  }

print "--------------------------- \n";

  my %r_hds = reverse %hds;
  foreach $value (values %hds) {
    print "key: $r_hds{$value} \n";
    print "value: $value \n";
  }

print "--------------------------- \n";

  foreach $key   (keys %hds) {
    print "key: $key \n";
    print "value: $hds{$key} \n";
  }


Here is the output:

Use of uninitialized value in concatenation (.) or string at h line 11.
key:
value: 0C8CB35F
Use of uninitialized value in concatenation (.) or string at h line 11.
key:
value: 0C9CB37D
---------------------------
key: 1
value: 0C8CB35F
key: 2
value: 0C9CB37D
---------------------------
key: 1
value: 0C8CB35F
key: 2
value: 0C9CB37D


--
regards, Richard
--
tmqrich...@gmail.com