All of the comments have either been: "that option doesn't do it", or "use a different module". Nobody managed to suggest either a fix/change for XML::Simple, or a set of options I can use that causes XML::Simple to become 'self-consistent' when dealing with partial content.

So in the end, I wrote a small post-processing routine to normalize the output from XMLin(). I.e recurse through the structure and a) promote leafs that are empty hashes to empty values.

 { } to  ''

and b) hashes that contain only the single 'content' entry into simply the value:

 { content => 'xxx' } to  'xxx'

Now I consistently get what I expected regardless of data content. 

$VAR1 = \{
            'obj' => [
                     {
                       'class' => 'myclass',
                       'set' => {
                                'key2' => '',
                                'key1' => 'a'
                              }
                     },
                     {
                       'class' => 'myclass',
                       'set' => {
                                'key2' => 'b',
                                'key1' => 'a'
                              }
                     }
                   ],
            'name' => 'me'
          };

[download]
Using the following: 
sub reduce {
  my ($ref) = @_;

  if (ref($ref) eq 'REF') {       # recurse into references...
    $$ref = reduce($$ref);
  } elsif (UNIVERSAL::isa($ref, 'HASH')) {
    my @keys = keys %$ref;
    if (scalar (@keys) == 0) {    # empty hash becomes an empty string
      return '';
    } elsif (scalar (@keys) == 1 && $keys[0] eq 'content') {
      $ref = $ref->{$keys[0]};    # 'content'-only becomes the value
    } else {
      foreach (keys %$ref) {      # recurse into multi-element hashes
        $ref->{$_} = reduce($ref->{$_});
      }
    }
  } elsif (UNIVERSAL::isa($ref, 'ARRAY')) {
    foreach (@$ref) {             # recurse into arrays
      reduce($_);
    }
  }
  return $ref;
}

[download]

In reply to Re: XML::Simple isn't listening to SuppressEmpty by fhew
in thread XML::Simple isn't listening to SuppressEmpty by fhew

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.