.he 'ERRFUN''Page %'
.fo 'Steven Hardy''January 78'
ERRFUN	This is a variable which is initialised to have SYSERR as its
value.  Whenever the POP11 system detects an error it calls ERRFUN with
the culprits and a 4 digit number, of which the first indicates the
number of culprits and the rest indicates the type of error, e.g.
4 + [] produces ERRFUN(4,[],2045); i.e. two culprits and ERROR 45.
You can redefine ERRFUN, for example:
.tp6
 	: FUNCTION ERRFUN();
 	:	[FOOL - YOU MADE A MISTAKE] =>
 	: END
