mismatch

mismatch is an alias for `cl-mismatch' in `cl.el'.

(mismatch SEQ1 SEQ2 [KEYWORD VALUE]...)

Compare SEQ1 with SEQ2, return index of first mismatching element.
Return nil if the sequences match. If one sequence is a prefix of the
other, the return value indicates the end of the shorter sequence.

Keywords supported: :test :test-not :key :start1 :end1 :start2 :end2 :from-end