perl6/doc/lib/Parcel
doc src
(title) class Parcel
class Parcel is Cool does Positional { }
I<Parcel> stands for I<Par>enthesis I<cel>l, ie an expression
surrounded by parenthesis. Though with the exception of the empty parcel,
() , it is really the comma that creates a Parcel.
(1 + 2) # not a Parcel
() # empty Parcel
(1,) # Parcel with one element
(1, 2) # Parcel with two elements
Parcels are immutable, but can contain mutable containers.
my $x;
my $p = (0, $x, 2); # can assign to $p[1], but not
# to any other element of $p
Word-quoting constructs such as < <... >> also create parcels:
<a b c> # 3-element Parcel
In flattening list context, parcels are flattened out and disappear:
my @flat = <a b>, <c, d>;
say @flat.elems; # 4
