 Unusual control flow can trigger mines, which cause control in performed procedures to return at unexpected times to unexpected locations. Procedures can be reached in three ways: they can be called with PERFORM, jumped to from a GO TO or through execution "falling through" the bottom of an above paragraph. Combinations of these invoke undefined behavior, creating mines. Specifically, mines occur when execution of a range of procedures would cause control flow to go past the last statement of a range of procedures already being performed.
