split-string is a compiled Lisp function in `subr'.
(split-string STRING &optional SEPARATORS)

Splits STRING into substrings where there are matches for SEPARATORS.
Each match for SEPARATORS is a splitting point.
The substrings between the splitting points are made into a list
which is returned.
If SEPARATORS is absent, it defaults to "[ \f\t\n\r\v]+".

If there is match for SEPARATORS at the beginning of STRING, we do not
include a null substring for that.  Likewise, if there is a match
at the end of STRING, we don't include a null substring for that.

Modifies the match data; use `save-match-data' if necessary.