modified version with just sleeps.

use Data::Dumper;

my %child_status=();
sub reaper {
    my $child;
    while (($child=waitpid(-1,WNOHANG))>0) {
        warn "signal: $child\n";
        $child_status{$child} = $? >> 8;
    }
}

sub copy {
    my $file = shift;
    my $dir  = shift;

    local $SIG{CHLD} = \&reaper;

    my $reader_pid = open( my $reader, '-|' );

    if ($reader_pid) {

    }
    else {
        exec 'sleep 301';
        exit;
    }
my $writer_pid;
    if ($writer_pid = fork()) {
        
    }
    else {
        chdir($dir);
        open( STDIN, "<&=" . fileno($reader) );
        exec 'sleep 302';
        exit;
    }

    while (1) {
        sleep 1;
        next if !%child_status;
               
print Dumper \%child_status;
warn "r $reader_pid, w $writer_pid\n";

        foreach my $pid ($reader_pid, $writer_pid) {
            if ($child_status{$pid} != 0) {


                %child_status = ();
                die  "failed tar\n";
            }
        }

        if (exists $child_status{$writer_pid} && exists $child_status{
+$reader_pid}) {
            last;
        }
    }

}

copy("/etc/hosts",".");
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