<p>Blocks of programming code can be understood according to the functions they serve, and these blocks can be saved for later reuse. When trying to grasp the functioning of large programs, it is important to understand blocks of code as functionally significant chunks, which this study refers to as "modules". Further, we position "structural understanding" as the ability to recognize and acquire significant blocks of code as modules, to recognize and acquire combinations of modules as larger modules, and to create combinations of these larger modules. We propose the Expandable Modular Statements Method as a learning support method for structural understanding in which learners first examine programs line-by-line to construct modules for each significant chunk of code and modify constructed modules by adding code or existing modules. Development and evaluation of a system employing this method demonstrate learner receptivity and the system's usefulness for structural understanding.</p>