ForceArray => 1 (in) (IMPORTANT!)
   This option should be set to ’1’ to force nested elements to be
   represented as arrays even when there is only one.  Eg, with
   ForceArray enabled, this XML:

       <opt>
         <name>value</name>
       </opt>

   would parse to this:

       {
         ’name’ => [
                     ’value
                   ]
       }

    instead of this (the default):

       {
         ’name’ => ’value
       }

   This option is especially useful if the data structure is likely to
   be written back out as XML and the default behaviour of rolling
   single nested elements up into attributes is not desirable.
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I am not really that concerned, as long as the DOM tree still keeps logically equivalent, although you can argure that a child is not a property, but well...

The first thing came up in my mind was this testing, which I felt interesting, mostly triggered by your post:

use XML::Simple;

use strict;
use warnings;

my $xml = XMLin('<config ip="127.0.0.1" port="12345"><timeout>1000</ti
+meout><timeout>2000</timeout></config>');
print XMLout($xml);
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The output was:

<opt ip="127.0.0.1" port="12345">
  <timeout>1000</timeout>
  <timeout>2000</timeout>
</opt>
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I am satisfied.

Are you happy that 'config' was replaced by 'opt'? If that is not the desired behaviour, instead write,

my $xml = XMLin(..., KeepRoot => 1);
print XMLout($xml, KeepRoot => 1);
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which would correctly output:

<config ip="127.0.0.1" port="12345">
  <timeout>1000</timeout>
  <timeout>2000</timeout>
</config>

The KeepRoot option tells XML::Simple that your structure already has a root node.

Just want to point out that the <timeout> element did not get fold up into attributes in your example is because there are more than one of them, by default if there is only one <timeout>, it will be folded up into an attribute.