# code: http://golf.shinh.org/reveal.rb?sort+by+first+occurrence/tails_1642141392&nbb
# target Nibbles version: 0.23
# commenter version: 0.1.2.181

+ #(concat):[[chr]] 
    =~ #(group by (also sorts)):[[[chr]]] 
        ;;@ #(= allLines):[[chr]] 
        ~ #(nosort):null 
        #(implicit arg = A):[chr] <--arg( A:[chr] )