Not sure what platform you are on, but if you are on OS X and have access to an OS X Server machine, grab a copy of macbin from /usr/bin/. You can use it to macbinarize and de-macbinarize files, and it is quite handy. Otherwise, as others have mentioned, Mac::Macbinary is a good approach. Supplying a correct file extension will help but you macbinarizing will preserve the resource fork & HFS metadata.