From the xar utilities source code, it looks like it can use either the expat or libxml2 XML parsers
#if HAVE_LIBXML_XMLREADER_H
#include <libxml/xmlreader.h>
#elif HAVE_BSDXML_H
#include <bsdxml.h>
#elif HAVE_EXPAT_H
#include <expat.h>
How do I get it to use expat instead of libxml when I install it using ports?