select((select($fh), $|=1)[0]);

##</code><code>##

use IO::Handle;    # update: not needed for Perl 5.14+
# ...
$fh->autoflush();

##</code><code>##

print $file $name, $rank, $serial_num, "\n";

##</code><code>##

print {$file} $name, $rank, $serial_num, "\n";

##</code><code>##

use IO::Handle;
$file->print( $name, $rank, $serial_num, "\n" );