Perl IO::Handle 指定autoflush，立即写入

autoflush 表示不缓冲，立即写入
use IO::Handle;
open my $fhw, '>', $filename;
$fhw->autoflush(1);
print $fhw $data1, "\n";
#....
print $fhw $datan, "\n";
close $fhw;