If on admin/config/development/performance/expire one sets it so that EXPIRE PROTOCOL does not include the base url, then the logic in the function boost_parse_url fails at

if (empty($parts['host']) || empty($parts['path'])) {
    return FALSE;

as parse_url will never return a host name and no pages will ever expire after editing.

Appears to also be further issues with expire on a multi-site if $parts['host'] is commented out, then the filename is returned with double forward slashes,


which is understandable as the hostname should appear in between, but logging the filename EXPIRE PROTOCOL HOST is enabled shows no expiry of any pages because of a missing / e.g. it searches for


and so also never expires an edited article.