#12821 leaves many questions open (code box at https://symfony.com/doc/4.4/routing.html#route-groups-and-prefixes)

• The PHP config doesn't show an example. Since Symfony is moving away from YAML towards PHP, there should be one. What's the starting point of the path - why does the first argument start with ../../, but this one with ../? After half an hour of trial and error, I couldn't get it to work ;-)
• What's the meaning of the curly braces in the pattern?
• When the text reads "use the optional fifth argument..." (changed to "fourth" in Update routing.rst #14506), there should be a hint on what to pass as third argument.