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    <p>First of all, always start every script or module with:</p> <pre><code>use strict; use warnings; </code></pre> <p>You will get more warning messages and sooner, which greatly helps debugging.</p> <p>I cannot duplicate your error: when I put that code into a file and run it with no additional flags, I get: <code>size = , position =</code>. <strike>There is no <code>$size</code> variable in the code you printed, so </strike> the error message does not match.</p> <p>Nevertheless, you are declaring your data structures incorrectly. Hashes and arrays can only contain scalar values, not lists: so if you want to nest an array or a hash, you need to make it a reference. See <a href="http://perldoc.perl.org/perldata.html" rel="nofollow noreferrer">perldoc perldata</a>, <a href="http://perldoc.perl.org/perldsc.html" rel="nofollow noreferrer">perldoc perldsc</a> and <a href="http://perldoc.perl.org/perlreftut.html" rel="nofollow noreferrer">perldoc perlreftut</a> for more about data structures and references.</p> <pre><code>my %photo_details = ( black_cat =&gt; [ { size =&gt; '1600x1200', position =&gt; -25 }, { size =&gt; '1280x1024', position =&gt; 25 }, { size =&gt; '800x600', position =&gt; 0 }, ], race_car =&gt; [ { size =&gt; '1600x1200', position =&gt; 10 }, { size =&gt; '800x600', position =&gt; 5 }, ], ); foreach my $photo_detail (@{$photo_details{black_cat}}) { my $size = $photo_detail-&gt;{size}; my $position = $photo_detail-&gt;{position}; print ("size = $size, position = $position\n"); } </code></pre>
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    1. POHow do I reference a Perl hash in an array in a hash?
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    1. COGood advice and explanation. All I would add is that the following is useful in debugging Perl data structure issues: use Data::Dumper; print Dumper(\%photo_details);
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    2. COI'm confused, $size definitely **is** in the snippet he posted, you even carried it over to your code. What did you mean?
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    3. CO@lexu: yes, you're right; I was thinking the error might have come from using `$photo_detail->{$size}` vs `$photo_detail->{size}`. I totally overlooked the `my $size = ...` declaration. Nevertheless, I can't duplicate the OP's error. With strictures enabled, the code barfs earlier, at `%photo_detail` not being declared (due to the for loop not dereferencing the array).
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