my $stdin = IO::Select->new(\*STDIN);
    open my $fh, '|-', $cmd or die $!;
    if (@ARGV || $stdin->can_read(0)) {
        while (<>) {
            print {$fh} $_ or die $!;
        }
    }
    else {
        print {$fh} "\n" or die $!;
    }
    close $fh or die $!;