When I have a list wich just one item and sublists, the node doesn’t work. The warning is “_Converting an array to var would cause array rank reduction and is not permitted”.
but if I have a list only with sublists (even if sublists have only one item), it works.
You could try it with “replace” nodes since your values are strings. Furthermore, they offer the possibility to play with levels. Try also those in DanEDU or Clockwork packages.
You found one of the limitations of imperative code - mixing singletons and lists can be tricky, you usually get a “Rank Reduction” exception. If you want to stick with nodes, one way to get around this is to manually use function mapping techniques: