Well, you'd get something like what you want by doing this:

$file_path =~ s#^$path##;
[download]

instead of this:

eval "$file_path =~ tr/$path//";
[download]

(heck, you could even do this, if you were in a silly mood:

($file_path) = split /$path/, $file_path, 1;
[download]

but I don't know that I'd recommend it)

but you might want to look in CPAN for better solutions to your underlying problem--they're out there.

By the way, you'll note that I used # instead of / for my separator--I almost always do that, especially when I've got lots of slashes in my pattern, as it makes it easier to see what's going on.

Update: I fixed some typos and stuff I didn't like.