Filter and sort associative array

[Head Scratcher]

Thank you. This works great. What I don't understand is how a 
key-value pair ends up being a set of strings. Where did the 
value of the key-value pair get removed?  According to the 
library documentation, the array function "allocates an array and 
initializes it with copies of the elements of range r." So 
wouldn't the resulting array contain pairs? And if so, how does 
the sort work on pairs?