Observe :)

$  perl -MXML::Twig -e " print XML::Twig->new( keep_spaces => shift)->
+parse( q{<header>Now <la>hist.</la> and <la>rare</la></header>} )->_d
+ump  "
document
|-header
| |-PCDATA:  'Now '
| |-la
| | |-PCDATA:  'hist.'
| |-PCDATA:  ' and '
| |-la
| | |-PCDATA:  'rare'
[download]

rare previous sibling is and

and previous sibling is hist

hist previous sibling is now

XML::Twig/http://search.cpan.org/dist/XML-Twig/MANIFEST, http://web.archive.org/web/20070819113402/http://www.xmltwig.com/tutorial/perl_xml/