1INCLAN: erract - variable for error handling

"erract" is a variable for error handling in macros. If an error occurs
within a macro, the value of erract is executed as a command. By default
the exit command is executed, i.e. the program returns to interactive
input. Errors that occur interactively are displayed and the program
continues with the execution of the next statement.

Example: set erract="show; quit"
         In case of an error in a macro a listing of all global variables
         is given, and the program is stopped. Such error handling can be
         useful if the program is used non-interactively.