How to extract local functions from within a .m file?

Use case: I have a UI which opens up a particular local function for a user using matlab.desktop.editor.openAndGoToFunction.

Now the user should have an option to save only the local function in a separate file. To do this, i need to have atleast have the starting and ending lines of a function, to do some sort of file read. Can go for regexp but could be costly in case of files where the local function is huge. Any recommendations/suggestions will be appreciated.