Perl6 REPL print behaviour

Question

When I execute the following statement in the Perl6 REPL:

my $var = 1, 2, 3;

it prints:

(1 2 3)

This seems curious to me, because $var is actually assigned a single integer (i.e. $var.WHAT returns (Int)), rather than a List of Ints.

I take it that the reason that an Int is assigned is the higher precedence of the item assignment operator (=) relative to the comma operator (,), which leaves the ,2,3 in sink context. But why does the REPL display a List of Ints? And what does the REPL in general display after the execution of a statement?

Answer 1

The REPL basically does a say (my $var = 1,2,3). Because the result of that expression is a List, it will show as (1 2 3). Inside that expression, only the first element of that list gets assigned to $a, hence it being an Int.

So why didn't it warn about that? This does, as you pointed out:

$ perl6 -e 'my $a = 1,2,3'
WARNINGS for -e:
Useless use of constant integer 2 in sink context (lines 1, 1)
Useless use of constant integer 3 in sink context (lines 1, 1)

whereas this doesn't:

$ perl6 -e 'say (my $a = 1,2,3)'
(1 2 3)

The reason is simple: because of the say, the ,2,3 are no longer in sink context, as they are being used by the say.