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    <p><strong><code>use strict; use warnings;</code></strong>. Always.</p> <p>Your hash declaration is not doing what you think it's doing, it has an odd number of elements.</p> <p>Try this:</p> <pre><code>use Data::Dumper; my %hash = ( 0=&gt; , 1=&gt;"Man"); print Dumper(%hash); </code></pre> <p>You'll see that <code>$hash{0}</code> is set to 1, <code>$hash{"Man"}</code> exists but is <code>undef</code>, and <code>$hash{1}</code> does not exist at all. i.e. your hash declaration is equivalent to:</p> <pre><code>my %hash = (0 =&gt; 1, "Man" =&gt; undef); </code></pre> <p><strong>Why</strong> is this happening? It's because:</p> <p><li> <code>=&gt;</code> is essentially an equivalent of <code>,</code><li> <a href="http://perldoc.perl.org/perldata.html#List-value-constructors" rel="nofollow">List value constructors</a> work that way, e.g. <code>($a,,$b)</code> is equivalent to <code>($a,$b)</code></p> <p>Relevant quotes from that document:</p> <blockquote> <p>The <strong><code>=&gt;</code></strong> operator is mostly just a more visually distinctive synonym for a comma, but it also arranges for its left-hand operand to be interpreted as a string if it's a bareword that would be a legal simple identifier. </p> </blockquote> <p>And:</p> <blockquote> <p>The null list is represented by <strong><code>()</code></strong>. Interpolating it in a list has no effect. Thus <strong><code>((),(),())</code></strong> is equivalent to <strong><code>()</code></strong>. Similarly, interpolating an array with no elements is the same as if no array had been interpolated at that point.</p> <p>(...)</p> <p>The list <strong><code>1,,3</code></strong> is a concatenation of two lists, <strong><code>1,</code></strong> and <strong><code>3</code></strong>, the first of which ends with that optional comma. <strong><code>1,,3</code></strong> is <strong><code>(1,),(3)</code></strong> is <strong><code>1,3</code></strong> (And similarly for <strong><code>1,,,3</code></strong> is <strong><code>(1,),(,),3</code></strong> is <strong><code>1,3</code></strong> and so on.) Not that we'd advise you to use this obfuscation.</p> </blockquote> <p>Apply this to your code:</p> <pre><code> (0 =&gt; , 1 =&gt; "Man"); is (0 , , 1 , "Man"); is (0 , 1 , "Man"); </code></pre>
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    1. POWhy is it printing all three printing statements?
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    1. COThe main point is that `=>` is merely syntactic sugar for `,`, which is why `0` gets mapped to `1` instead of to `undef`
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      1. USNathan Fellman
    2. COI didn't even know one cat write horrible things like `(1,,,,,,,2)` in `perl` prior to this post.
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      1. USDallaylaen
    3. COOr even "horribler" `(1=>=>=>=>=>2)` - mix in comas if you feel adventurous :-)
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