There can be an arbitrary number of whitespaces after the function handle.  But in the tmLanguage there is a limit on 4 whitespace characters. Also `\s` includes newlines, which is not allowed.  https://github.com/mathworks/MATLAB-Language-grammar/blob/4f1c0c8e8eac1494ee9c2bac18605aca08b08806/Matlab.tmbundle/Syntaxes/MATLAB.tmLanguage#L2491