The structured Loop is one of the most commonly used iteration pattern. This gives the user ability to execute a task or a set of tasks repeatedly based on a pretest or post-test construct. The loop structure has a single entry and exit point. In BPMN, structured loops can be created by simply connecting XOR gateway with an upstream activity.
In this example, unless one of the credit cards is accepted, the user cannot get gas. The user does have a choice to provide any number of credit cards until one of them gets accepted.