Users of the Unicode::Map perl module may have discovered a problem when attempting to convert Big5 text. The problem is that non-chinese (ascii, roman) characters will not be converted (they will be dropped instead), and in some cases will corrupt neighboring chinese characters. The solution seems to be to use the CP950 mapping instead, which is a Microsoft implementation of Big5. I don't know why (probably an oversight), but this mapping seems to include basic ascii in addition to the chinese characters.
I don't speak Chinese, and am not a character encoding expert, so I welcome English-language corrections.