WHEN EXCEPTION USE and HANDLER

Exception handling process can be described as an internal procedure so that more than one when-block has an identical exception-handler in common.

An exception handler described as an internal procedure is called a detached handler.
A detached handler begins with a HANDLER line and ends with an END-HANDLER line.
A HANDLER line holds a name of the handler. The rule for naming a handler is same as that of a numerical variable.
When you use a detached handler, replace WHEN EXCEPTION IN ~ USE ~ END WHEN with WHEN EXCEPTION USE ~ END WHEN. A WHEN-EXCEPTION-USE line holds the name of the detached handler.
Example

100 WHEN EXCEPTION USE h
110    PRINT 1/A
120 END WHEN
130 WHEN EXCEPTION USE h
140    PRINT SQR(-1)
150 END WHEN
160 HANDLER h
170    PRINT EXTYPE
180 END HANDLER
190 END