# code: http://golf.shinh.org/reveal.rb?Duplicate+characters/darrenks_1642094651&nbb
# target Nibbles version: 0.21
# commenter version: 0.1.2.181

+ #(concat):[chr] 
    . #(map):[[chr]] 
        allInput #(;_):[chr] 
        \A 
        : #(append):[chr] 
            #(implicit arg = A):chr 
            #(implicit arg = A):chr