clarify that N comes from $of, colomon++

Author: TimToady

S32-setting-library/Containers.pod

@@ -579,7 +579,7 @@ C<.comb> on that string with the same parameters. See C<Str::comb>.
  multi method combinations ( Int $of )
  multi method combinations ( Range $of = 1 .. +self )
 
-Returns all combinations of the list taken N at a time.  If the
+Returns all combinations of the list taken N at a time (specified by the C<$of> parameter).  If the
 range option is taken, returns all subset combinations in order of
 increasing size.  The return value is a list of (presumably immutable)
 array values.  (Note: When used on actual sets and other iterable