Complex sentence: Under this model, a preferred approach to repetative tasks is to create a function or subroutine that performs single pass through the task; this subroutine is then called by the parent routine, either repetatively or better yet, with some form of looping structure.
Split into simpler sentences: Under this model, a preferred approach to repetative tasks is to create a function or subroutine that performs one pass through the task. This subroutine is then called by the parent routine, either repetatively or better yet, with some form of looping structure.