I pinned down the problem to the data file itself because I can download other files outside of cgi-bin to the client. I suspected the data file was somehow damaged when I got it. But I still can open in a text editor. And strange enoght, I can open it in a local perl script!

I also tested that it is not because the data file is too large as nobull suggested. Thanks for gam3 for reminding me that to use file path in '' with one backslash. It is much easy to read and comfortable.

Thank you all again for giving advices on this question. It is helpful. Really appreciate it!