# code: http://golf.shinh.org/reveal.rb?One+char+CAT/tails_1644212990&nbb
# target Nibbles version: 0.23
# commenter version: 0.1.2.181

/ #(foldr1):chr 
    @ #(= fstLine):[chr] 
    #(implicit arg = B):chr <--arg( B:chr A:chr )