# code: http://golf.shinh.org/reveal.rb?Shifting+Pattern+Fixed/tails_1646611779&nbb
# target Nibbles version: 0.25
# commenter version: 0.1.2.181

`. #(iterate while uniq):[[chr]] 
    @ #(= fstLine):[chr] 
    : #(append):[chr] <--arg( A:[chr] ) 
        `( #(uncons):chr -->let( B:[chr] ) 
            \ #(reverse):[chr] 
                $ #(= A):[chr] 
        \ #(reverse):[chr] 
            #(implicit arg = B):[chr]