handleerror - Default error handler
handleerror is the default error handler.
It issues error messages according to the
state of the errordict.
The command that caused the error is left at the
top of the dicitonary stack.

An error is raised by the command
/func /error raiseerror

The flag newerror helps to distinguish between interrupts caused
by call of stop and interrupts raised by raiseerror.
It also helps to find errors in the handler itself. This is
why it should be re-set to false at the very end of the handler!

Examples: To catch errors from an unknown function f,
one can write:

{f} stopped {handleerror} if

The Red Book  
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