.he 'CANCEL''Page %'
.fo 'Steven Hardy''January 78'
CANCEL
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This cancels all words following it up to (but not including) the first 
semi-colon.  The mechanics of cancellation are
complex and you should rarely (if ever) need to use it.  It's effect is that
any identifier cancelled can be used afresh with no
thought to its use in the past.  Any existing references to the identifier
will still refer to the old usage - any new use is
independent.
(see the entry for Oblist in the POPMESS demo.
If you wish to define a function whose name is already
used by the POP11 system (e.g. LENGTH) you will first have to CANCEL
it.
