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end_of_file.can be entered to return from the break environment. If the -t toplevel command line option is given, this goal is started instead of entering the default interactive top level (prolog/0).
Notably the gui based versions (swipl-win on Windows and MacOS) provide the menu Run/New thread that opens a new toplevel that runs concurrently with the initial toplevel. The concurrent toplevel can be used to examine the program, in particular global dynamic predicates. It can not access global variables or thread-local dynamic predicates (see thread_local/1) of the main thread.