Mention the cancellation feature of ThreadPoolScheduler.cue

Author: lizmat

doc/Type/Scheduler.pod6

@@ -27,10 +27,12 @@ code that is being scheduled and run.
 
 =head2 method cue
 
-    method cue(&code, Instant :$at, :$in, :$every, :$times = 1; :&catch)
+    method cue(&code, Instant :$at, :$in, :$every, :$times = 1; :&catch -> $cancelation)
 
-Schedules a callable (C<&code>) for execution. The adverbs control when and
-how the code is run:
+Schedules a callable (C<&code>) for execution and returns an instantiated
+C<Cancellation> object to cancel the scheduling of the code for execution
+(which is especially important if you specify the C<every => time> named
+parameter. The adverbs control when and how the code is run:
 
 C<$at> can be an L<Instant|/type/Instant> before which the code won't be run.
 Alternatively C<$in> is the number of seconds (possibly fractional) to wait
@@ -49,6 +51,9 @@ C<$times> tells the scheduler how many times to run the code.
 C<&catch> is called with the L<Exception|/type/Exception> as its sole argument
 if C<&code> dies.
 
+One should call the C<cancel> method on the returned C<Cancellation> object
+to cancel the (possibly repeated) cueing of the code.
+
 =end pod
 
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