$ perl -MIO::Select -E' open(my $fh, ">", "file") or die $!; my @r = IO::Select->new($fh)->can_read(); 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