Currently, URL hints appear to walk the tree for start- matches. so, whatever you type is searched as a prefix and it matches the search space of all the possible suffix extensions beyond this point which could match, I believe sorted by recency/frequency.
Say I have www.reddit.com/r/ScotLand/new
and I want to find r/Europe/new
I have to wipe out ALL of .../ScotLand/new to begin to match Europe/new.
I should be able to replace the "word" /Scotland/ with /Europe/ and have it do string-match on the LHS of my type point, finding the matches which extend to cover the RHS