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ḲJɓḲ⁾""j$€⁹¦Kð€Y - Link: list of characters, S
Ḳ - split (S) at spaces -> A
J - range of length -> I = [1,2,...len(A)]
ɓ ð€ - for each (i in I) with swapped arguments -> [f(S, 1), f(S,2), ...]
Ḳ - split (S) at spaces -> B
€ ¦ - sparse application...
⁹ - ...to indices: chain's right argument, i
$ - ...action: last two links as a monad:
⁾"" - literal list of characters = ['"', '"']
j - join (with B[i]) -> (e.g. with ['i','s']) ['"','i','s','"']
K - join with spaces
Y - join with newlines