We need a "immutable list" type (Parcel?)

Note that we're likely to need a separate type to represent
immutable lists, and which will be produced using infix:<,> .
The naming is open for discussion/bikeshedding.

S07-glr-draft.pod

@@ -160,7 +160,20 @@ parenthesized comma lists react to things like C<.elems> and C<.[]>.
 
     (1, (2, 3)).elems             # (pre-GLR) 3; (post-GLR) 2
     (1, 2, 3..7).elems            # (pre-GLR) 7; (post-GLR) 3
-
+
+Update 2015-06-22:  Okay, I'm no longer certain that C<Parcel> is
+disappearing.  We really need two types here; one (base) type that
+represents immutable lists, and another type that represents mutable
+lists.  The C<< infix:<,> >> operator would produce the immutable type.
+
+So, one possibility is to have C<Parcel> as a base class with C<List>
+as a derived class; another possibility is to have C<List> as the
+(immutable) base class and introduce another name for the mutable one.
+I suspect that the immutable form is the one that occurs most commonly,
+so there's an argument to be made that it should be called C<List>.
+
+C<Seq> might be another candidate name.
+
 =item *
 
 The C<for> statement will no longer flatten the value provided to it.