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    <p>Sonam:</p> <p>I've reedited your post in order to help format it for reading. Study the <a href="https://stackoverflow.com/editing-help">Markdown Editing Help Guide</a> and that'll make your posts clearer and easier to understand. Here are a couple of hints:</p> <ul> <li>Indent your code by four spaces. That tells Markdown to leave it alone and don't reformat it.</li> <li>When you make a list, put astricks with a space in front. Markdown understands it's a bulleted list and formats it as such.</li> </ul> <p>Press "Edit" on your original post, and you can see what changes I made.</p> <hr> <p>Now on to your post. I'm not sure I understand your <em>data</em>. If your data was in a hash, the keys would be unique. You can't have duplicate keys in a hash, so where is your data coming from?</p> <p>For example, if you're reading it in from a file with two numbers on each line, you could do this:</p> <pre><code>use autodie; use strict; use warnings; open (my $data_fh, "&lt;", "$fileName"); my %hash; while (my $line = &lt;$data_fh&gt;) { chomp $line; my ($key, $value) = split /\s+/, $line; $hash{$key}++; } foreach my $key (sort keys %hash) { print "$key appears $hash{$key} times\n"; } </code></pre> <p>The first three lines are <a href="http://perldoc.perl.org/index-pragmas.html" rel="nofollow noreferrer">Perl pragmas</a>. They change the way Perl operates:</p> <ul> <li><code>use autodie</code>: This tells the program to die in certain circumstances such as when you try to open a file that doesn't exist. This way, I didn't have to check to see if the <code>open</code> statement worked or not.</li> <li><code>use strict</code>: This makes sure you have to declare your variables before using them which helps eliminate 90% of Perl bugs. You declare a variable <strong><em>most of the time</em></strong> using <code>my</code>. Variables declared with <code>my</code> last in the block where they were declared. That's why <code>my %hash</code> had to be declared before the while block. Otherwise, the variable would become undefined once that loops completes.</li> <li><code>use warnings</code>: This has Perl generate warnings in certain conditions. For example, you attempt to print out a variable that has no user set value.</li> </ul> <p>The first loop simply goes line by line through my data and counts the number of occurrences of your key. The second loop prints out the results.</p>
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    1. POHow to count duplicate key and add all values of duplicate key together to make new hash with non duplicate key?
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    1. USDavid W.
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    1. COthank you so much it was a great help
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