Replace mention of "container type" by "type of variable"

If you sav "my %h is Bag", your changing the type of the "%h" variable,
which is *not* a container (aka, not a Scalar, Proxy or xxLexRef).

Author: lizmat

doc/Language/variables.pod6

@@ -49,22 +49,28 @@ Examples:
     my @array  = 1, 2, 3;   # Array variable with three elements
     my %hash   = London => 'UK', Berlin => 'Germany';
 
-X<|is (container type)>
-The container type can be set with C<is> in a declaration.
+X<|is (type of variable)>
+The type to which the variable will be bound, can be set with C<is> in the
+declaration of the variable.  Assuming we have a C<FailHash> class:
 
     class FailHash is Hash {
         has Bool $!final = False;
         multi method AT-KEY ( ::?CLASS:D: Str:D \key ){
             fail X::OutOfRange.new(:what("Hash key"), :got(key), :range(self.keys)) if $!final && !self.EXISTS-KEY(key);
-            callsame
+            callsame  # still not final, so do normal action from Hash
         }
 
         method finalize() {
             $!final = True
         }
     }
 
+One can then define a C<%h> variable using C<is>:
+
     my %h is FailHash = oranges => "round", bananas => "bendy";
+
+And then run the following code:
+
     say %h<oranges>;
     # OUTPUT: «round␤»
     %h.finalize;