Explains success closes #905

doc/Language/phasers.pod6

@@ -15,7 +15,7 @@ known as I<phasers>, since they generally mark the transition from one phase of
 computing to another. For instance, a C<CHECK> block is called at the end of
 compiling a compilation unit. Other kinds of phasers can be installed as well;
 these are automatically called at various times as appropriate, and some of
-them respond to various control exceptions and exit values.
+them respond to various control exceptions and exit values. For instance, some phasers might be called if the exit from a block is successful or not, with I<success> in this case defined by returning with a defined value or list without any C<Failure> or exception in the process.
 
 Here is a summary:
 
@@ -44,7 +44,7 @@ CONTROL {...} #  catch control exceptions, before LEAVE
    QUIT {...} #  catch async exceptions within a whenever-block, runs very last
 
 COMPOSE {...} #  when a role is composed into a class
-CLOSE   {...} #  appears in a supply block, called when the supply is closed
+  CLOSE {...} #  appears in a supply block, called when the supply is closed
 =end code
 
 Phasers marked with a C<*> have a run-time value, and if evaluated earlier than