20.4 Protected operations and the block construct

In this section, we describe how to use block to protect sections of Dylan code from unexpected nonlocal exits. Dylan provides powerful ways to execute nonlocal exits from a given execution context. An application might signal a condition that might cause a handler to execute a nonlocal exit, or an application might call an exit procedure named by the first argument to block. Sometimes, it is necessary to add behavior to the nonlocal exit, to keep the application's execution environment in good shape.