text: user9988: My third year comp sci friend got me this far, I hope you guys can help me with the last inch! For the record, I have practically no coding experience. I am using the 3.9.4 alpha version of MUMmer.
  Here is the manual I have been following: http://mummer.sourceforge.net/examples/
  I am at part 2.2.2 Running the Mummer plot, and I type in the final line to generate the plot.
  I type:
  mummerplot -x "[0,8666124]" -y "[0,9025688]" -postscript -p mummer mummer.mums
  And the error is:
  Can't use 'defined(%hash)' (Maybe you should omit the defined ()?) at /usr/bin/mummerplot line 884
  
  Line at 884:
  if ( defined (%$rref) ) {                                                                                                            #-- skip reference sequence or set atts from hash
          if ( !exists ($rref->{$idR}) ) { next; }
          else { ($refoff, $reflen, $refdir) = @{$rref->{$idR}}; }
  
  Its perl
  
  user10594: I had the same error and I solved by removing defined and writing only if (%$rref) in the mummerplot code. You have to do this for all the lines that you have it. There should be six lines to correct in this way .
  You can find an explanation of why here, that tells that the function defined:
  
  Returns a Boolean value telling whether EXPR has a value other than the undefined value undef. If EXPR is not present, $_ is checked.
  
  And then:
  
  Use of defined on aggregates (hashes and arrays) is no longer supported. It used to report whether memory for that aggregate had ever been allocated. You should instead use a simple test for size:
  if (%a_hash)   { print "has hash members\n"   } 
  
  
original_text: 9988: <p>My third year comp sci friend got me this far, I hope you guys can help me with the last inch! For the record, I have practically no coding experience. I am using the 3.9.4 alpha version of MUMmer.</p>
  <p>Here is the manual I have been following: <a href="http://mummer.sourceforge.net/examples/" rel="nofollow noreferrer">http://mummer.sourceforge.net/examples/</a></p>
  <p>I am at part 2.2.2 Running the Mummer plot, and I type in the final line to generate the plot.</p>
  <p>I type:</p>
  <p><code>mummerplot -x &quot;[0,8666124]&quot; -y &quot;[0,9025688]&quot; -postscript -p mummer mummer.mums</code></p>
  <p>And the error is:</p>
  <pre><code>Can't use 'defined(%hash)' (Maybe you should omit the defined ()?) at /usr/bin/mummerplot line 884
  </code></pre>
  <p>Line at 884:</p>
  <pre><code>if ( defined (%<span class="math-container">$rref) ) {                                                                                                            #-- skip reference sequence or set atts from hash
          if ( !exists ($rref-&gt;{$idR}) ) { next; }
          else { ($refoff, $reflen, $refdir) = @{$rref-&gt;{$</span>idR}}; }
  </code></pre>
  <p>Its perl</p>
   10594: <p>I had the same error and I solved by removing <code>defined</code> and writing only <code>if (%$rref)</code> in the mummerplot code. You have to do this for all the lines that you have it. There should be six lines to correct in this way .</p>
  <p>You can find an explanation of why <a href="https://perldoc.perl.org/functions/defined" rel="nofollow noreferrer">here</a>, that tells that the function <code>defined</code>:</p>
  <blockquote>
  <p>Returns a Boolean value telling whether EXPR has a value other than the undefined value undef. If EXPR is not present, $_ is checked.</p>
  </blockquote>
  <p>And then:</p>
  <blockquote>
  <p>Use of <code>defined</code> on aggregates (hashes and arrays) is no longer supported. It used to report whether memory for that aggregate had ever been allocated. You should instead use a simple test for size:
  <code>if (%a_hash)   { print &quot;has hash members\n&quot;   } </code></p>
  </blockquote>
  