Problem: interleave first every third

Code: interleave+first+every+third/tails_1723008733

Nibbles version: 0.2 | 0.21 | 0.22 | 0.23 | 0.24 | 0.25 | 1.00

Format: Compact | Simple | +Type | Table | JSON | .nbl (DeBruijn) | .nbl (names)

: (append) 
    + (concat) 
        . (map) 
            `/ (chunks of) 
                ~ (auto = 2) 
                `) (swapped uncons) -->let( A ) 
                    @ (= fstLine) 
            : (append) <--arg( B ) 
                @ (= A) 
                (implicit arg = B) 
    (implicit arg = A)