BREAK
Used inside a SELECT/WHEN condition, exit unconditionally before the end of When condition, that is go to the instruction following ENDSEL.
NOBREAK
Usually, when a SELECT/WHEN condition is satisfied, only the first satisfied condition is executed. Used inside a Select/When condition, with NOBREAK instruction, a branch is done of the following WHEN condition and, if satisfied, is executed. Usually is used as a last statement of the WHEN block; the effect is to transfer control to the next WHEN condition.