1. A method for comparing two modules, the method being performed by a computer system which includes a storage device that stores the modules, wherein each of the modules includes a plurality of sentences written in a programming language, wherein the plurality of sentences of the module includes a plurality of conditional statements, wherein each of the plurality of conditional statements has at least one of an executable-on-satisfaction statement and an executable-on-failure statement, wherein the executable-on-satisfaction statement is one of the plurality of sentences that is executed when a conditional expression of the corresponding conditional statement is satisfied, and the executable-on-failure statement is another one of the plurality of sentences that is executed when the conditional expression is not satisfied, wherein at least one of the plurality of conditional statements has another one of the plurality of conditional statements therein as at least one of the executable-on-satisfaction statement and the executable-on-failure statement so that the plurality of conditional statements form a specifiable hierarchical structure of the module, the method comprising: obtaining a first module and a second module from the storage device, wherein the first module is one of the two modules, and the second module is another one of the two modules; and creating a message which shows whether the hierarchical structure of the first module is identical to the hierarchical structure of the second module or not; wherein the hierarchical structure of each module is a combination of hierarchy depths involved in the module, wherein each hierarchy depth indicates a depth with respect to a sentence at a top of the module.