[perl #130291] Proc::Asyn sends empty trying to stderr/stdout tap on program exit, even though the program did not send anything

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# New Ticket Created by  Александр Кирюхин 
# Please include the string:  [perl #130291]
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The original example to reproduce:

use v6;

my $p = Proc::Async.new('ls', '-l');

$p.stdout.tap(-> $v { say $v });
$p.stderr.tap(-> $v { say $v.WHAT; say $v.perl; }); # Prints (Str) and
empty string..

await $p.start;

Stdout and stderr is tapped with empty output on any command.