iswitchb-word-matching-substring

iswitchb-word-matching-substring is a compiled Lisp function in `iswitchb.el'.

(iswitchb-word-matching-substring WORD)

Return part of WORD before 1st match to `iswitchb-change-word-sub'.
If `iswitchb-change-word-sub' cannot be found in WORD, return nil.