# code: http://golf.shinh.org/reveal.rb?Relationship+ranking/tails_1665635773&nbb
# target Nibbles version: 1.00
# commenter version: 0.1.2.181

+ #(concat):[chr] 
    =~ #(group by (also sorts)):[[chr]] 
        @ #(= fstLine):[chr] 
        , #(length):int <--arg( A:chr ) 
            = #(subscript (wrapped)):[chr] 
                2 #(integer):int 
                `% #(split list (keep empties)):[[chr]] 
                    _ #(= fstLine):[chr] 
                    #(implicit arg = A):chr