How to add expressions, for example, the following to the translation (XLIFF format):
Click <a href='http://example.com'>here</a> to continue.
Could you put it in the CDATA field in xml? http://en.wikipedia.org/wiki/CDATA
In Twig, you can enable translation and disable autoescape, but you have to control your content as this may be a security flaw ...
{% autoescape false %}{{ 'your.translation.id'|trans }}{% endautoescape %}