What you see in the output depends on your terminal and few other things like locale and font.
Perl can only take sequence of bytes and manipulate it. It is the work of some other program
to draw a character on the screen that corresponds to that sequence of bytes. Assuming that D6 D0 is sequence for character 中 in GB-2312 encoding, the program produces sequence of bytes for the same character in UTF-8 encoding. If your terminal expects characters in GB-2312 encoding, then it won't display correct character. For example, my terminal expects text in UTF-8 encoding, so everything is displayed correctly.
I can not know what your terminal expects, but if the following simple program produces correct output, then your terminal expects GB-2312 encoding for the text.
perl -e 'print pack("H*", "D6D0"), "\n"'