$ perl -E'
    open(my $fh, ">", "file") or die $!;
    my $rv = sysread($r[0], $buf, 100);
    if (!defined($rv)) {
        say "Error: $!";
    } elsif (!$rv) {
        say "eof";
    } else {
        say "Got $rv bytes";
    }
'
Error: Bad file descriptor