From type/Channel

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method send(Channel:D: \item)

Enqueues an item into the Channel. Throws an exception of type X::Channel::SendOnClosed if the channel has been closed already. This call will not block waiting for a consumer to take the object. There is no set limit on the number of items that may be queued, so care should be taken to prevent runaway queueing.

my $c = Channel.new;
$c.send(1);
$c.send([2, 3, 4, 5]);
$c.close;
say $c.list; # OUTPUT: «(1 [2 3 4 5])␤»