Personally, I just use "mv -i file_to_delete ~/.Trash".

That's basically what this script does, but with two enhancements:
(1) less typing.
(2) it won't copy a 30GB file from /Volumes/MyBigFiles/file_to_trash into your home folder.

The hint explains what its for at the beginning, fyi.

I'm sorry; I did get the point of your code and didn't mean to be critical, but in hindsight I see that it could be taken that way (particularly on the Internet). Mostly I just wanted to see if anyone would respond with "Oh, you're not supposed to do that because it breaks X and Y." I don't normally work with multiple volumes (other than disk images), but if I start I will keep your solution in mind!