Side note on this function: if you extend.split a line not containing any of the S.Separators you will still get the line in the resulting table. This is not the same as an extend.range for instance.
Script to illustrate this case: https://try.lokad.com/s/extend.split

Sorry my link was private, please find here the shareable one: https://try.lokad.com/s/extend_split_example