Hash - keys must be unique

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Hashes example from a Well House Consultants training course
More on Hashes [link]

This example is described in the following article(s):
• Fresh Perl Teaching Examples - part 2 of 3 - [link]

Source code: fwom Module: P211

=head1 More about hashes

The keys of a Perl Hash must be unique, but the values don't
have to be.

The => operator is a pseudonym for , ... and it can be used
in the definition of a hash to help you tell the keys and
values apart when you come back to the code later. My group
from the course on which this was written fell about in fits
of laughter as we tried to work out if "Ashley Green" was a
place in Hertfordshire or a person.

If you use =>, then the string to the left may be a bare word -
in other words, you can leave the " marks off it unless it
contains spaces or special characters.

The elements in a hash are indexed using a "hashing technique"
that we explained during the course. This means that you can
get to any element you want quickly via its key, but you cannot
sort the hash. What you do, instead, is to sort a list of the
keys and this code shows two examples - sorting by key, and
sorting THE KEYS by the values they point to.

=cut

%locations = (
        Jerry => "Stevenage",
        Anup => "Basingstoke",
        "Ann Marie" => "Basingstoke",
        Andrew => "Wokingham",
        Justin => "Tidworth") ;

$locations{Graham} = "Melksham";
$locations{Lisa} = "Melksham";

@kkk = keys(%locations) ;
foreach $k (@kkk) {
        print "$k lives in $locations{$k}\n";
        }

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

@kkk = sort(keys(%locations)) ;
foreach $k (@kkk) {
        print "$k lives in $locations{$k}\n";
        }

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

@kkk = sort {$locations{$a} cmp $locations{$b}}
        (keys(%locations)) ;
foreach $k (@kkk) {
        print "$k lives in $locations{$k}\n";
        }

__END__

Output:

Dorothy-2:j10p grahamellis$ perl fwom
Anup lives in Basingstoke
Lisa lives in Melksham
Andrew lives in Wokingham
Ann Marie lives in Basingstoke
Jerry lives in Stevenage
Justin lives in Tidworth
Graham lives in Melksham
--------------------------
Andrew lives in Wokingham
Ann Marie lives in Basingstoke
Anup lives in Basingstoke
Graham lives in Melksham
Jerry lives in Stevenage
Justin lives in Tidworth
Lisa lives in Melksham
Dorothy-2:j10p grahamellis$

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