use XML::Smart ;

my $xml = XML::Smart->new(q`
<nl>
  number list 1
  number list 2
  <ul>
    unnumbered list1 
    unnumbered list 2
    <pl>
      plain list 1
      plain list 2
      <nl>
        numbered list 1
        numbered list 2
      </nl>
    </pl>
  </ul>
</nl>
` , 'html');

my $new_xml = XML::Smart->new() ;

process($xml , $new_xml) ;

print $new_xml->data ;


sub process {
  my $xml = shift ;
  my $new_xml = shift ;
  
  foreach my $node_i ( $xml->nodes ) {
    my @lines = split(/\s*\n\s*/ , $node_i) ;
    
    my $type ;
    if    ( $node_i->key eq 'nl' ) { $type = 'numbered' ;}
    elsif ( $node_i->key eq 'ul' ) { $type = 'unnumbered' ;}
    elsif ( $node_i->key eq 'pl' ) { $type = 'plain' ;}

    my $set_root = 1 if $new_xml->base->null ;

    $new_xml->{list}{type} = $type ;

    $new_xml = $new_xml->{list} if $set_root ;
    
    push( @{$new_xml->{'list-item'}} , @lines) ;
    
    process($node_i , $new_xml->{listitem} ) ;
  }
}


##</code><code>##

<?xml version="1.0" encoding="iso-8859-1" ?>
<?meta name="GENERATOR" content="XML::Smart/1.5.9 Perl/5.006001 [MSWin32]" ?>
<list type="numbered">
  <list-item>number list 1</list-item>
  <list-item>number list 2</list-item>
  <listitem>
    <list type="unnumbered"/>
    <list-item>unnumbered list1</list-item>
    <list-item>unnumbered list 2</list-item>
    <listitem>
      <list type="plain"/>
      <list-item>plain list 1</list-item>
      <list-item>plain list 2</list-item>
      <listitem>
        <list type="numbered"/>
        <list-item>numbered list 1</list-item>
        <list-item>numbered list 2</list-item>
      </listitem>
    </listitem>
  </listitem>
</list>

##</code><code>##

<list type="numbered">
  <list-item>number list 1</list-item>
  <list-item>number list 2</list-item>
</list>

##</code><code>##

<listitem>
  <list type="numbered"/>
  <list-item>numbered list 1</list-item>
  <list-item>numbered list 2</list-item>
</listitem>

##</code><code>##

<list type="numbered">
  <item>number list 1</item>
  <item>number list 2</item>
  <list type="unnumbered"/>
    <item>unnumbered list 1</item>
    <item>unnumbered list 2</item>
    <list type="plain"/>
      <item>plain list 1</item>
      <item>plain list 2</item>
      <list type="numbered"/>
        <item>numbered list 1</item>
        <item>numbered list 2</item>
      </list>
    </list>
  </list>
</list>