How to exclude when meta_key does not match or exist?

I’m making a site, where I want to list subpages. This plugin seems to do the job. However I want to exclude certain pages. Rather than manually listing page IDs, I would like to use an excluding meta key. Say, if I add to page a Custom Field “exclude-from-page-list” with a value “true”, the page would not be included. If a page has not that custom field at all or with a different value, it would be included. Can this be achieved and how?

TIA