interactor gets ignored, and this should be a valid skeleton element.
When done with skeleton, but before going back to `_'-point, add
-a newline (unless `skeleton-end-newline' is non-nil) and run the
-hook `skeleton-end-hook'.
+a newline (unless `skeleton-end-newline' is nil) and run the hook
+`skeleton-end-hook'.
SKELETON is made up as (INTERACTOR ELEMENT ...). INTERACTOR may be nil if
not needed, a prompt-string or an expression for complex read functions.