sure it's a cludge and there's a better way, but why split when you can just do:

$file="C:/aplle/index.htm";
$file=~ s/(.| )*\///; # delete everything(!) upto the last /
print $file;
[download]

and to answer your question there AM, you have to escape a / if you use it in a regex because there are /'s as the separator. Naturally if your slash goes the other way (and there is no shame in that) you still have to escape it because perl thinks you are escaping the character after the \.
-phill