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Use of hashes in Perl / CGI
Hashes example from a Well House Consultants training course
More on Hashes [link]

This example is described in the following article(s):
   • Why would you want to use a Perl hash? - [link]

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Source code: blx.pl Module: P211
#!/usr/bin/env perl

# Use of hashes in Perl / CGI

print "Content-type: text/plain\n\n";

while (<DATA>) {
        ($letter,$descript) = /^(\w) - (.*)/;
        $section{$letter} = $descript;
}

open FH,"/home/wellho/public_html/resources/mtable.txt";
while (<FH>) {
        chop;
        ($ref,$about) = split(/\s+/,$_,2);
        $lookup{$ref} = $about;
}

open FH,"/home/wellho/include/bloglinks.txt";
while (<FH>) {
        chop;
        ($ref,$mod) = split;
        $counter{$mod}++;
        }

open FH,"/home/wellho/include/bloglinks.txt";
while (<FH>) {
        chop;
        ($ref,$mod) = split;
        $latest{$mod} = $ref;
}

open FH,"/home/wellho/include/bloglinks.txt";
while (<FH>) {
        chop;
        ($ref,$mod) = split;
        $keyletter = substr($mod,0,1);
        if ($section{$keyletter}) {
                if ($thisarticle{$ref}{$keyletter}++ == 0) {
                        $sectcounter{$keyletter}++;
                }
        } else {
                $sectcounter{$mod}++;
        }
}

# When did I last talk about THAT?

print "\nWhen did I last talk about THAT?\n";
for (sort {$latest{$b} <=> $latest{$a}} keys(%latest)) {
        print "$_ - $latest{$_} - $lookup{$_}\n";
        }

# How many times have I talked about THAT?

print "\nHow many times have I talked about THAT?\n";
for (sort {$counter{$a} <=> $counter{$b}} keys(%counter)) {
        print "$_ - $counter{$_} - $lookup{$_}\n";
        }

# How many times have I talked about THAT - by major section

print "\nHow many times have I talked about THAT - by major section\n";
for (sort {$sectcounter{$b} <=> $sectcounter{$a}} keys(%sectcounter)) {
        if (/^.$/) {
                print "$_ - $sectcounter{$_} - $section{$_}\n";
        } else {
                print "$_ - $sectcounter{$_} - $lookup{$_}\n";
        }
}

# What have I NEVER talked about?
#
print "\nWhat have I NEVER talked about?\n";
for (keys %lookup) {
        unless ($counter{$_}) {
                print "$_ - $lookup{$_}\n";
        }
}
print "\n";

__END__
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Learn about this subject
This module and example are covered on the following public courses:
 * Perl Programming
 * Perl bootcamp
 * Learning to program in Perl
 * Perl Programming
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Perl are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Hashes" training module. You'll find a description of the topic and some other closely related examples on the "Hashes" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre or under an Open Training Notes License from our sister site http://www.training-notes.co.uk.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

Purpose of this website
This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

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This web site is written and maintained by Well House Consultants.

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Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

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