If you may need the filename later on:

my ($directory) = $fullpath =~ m|^(.*/)?|;
[download]

This will slurp as much as it can, as long as it's followed by a slash. $directory will be undefined if there isn't one in there... Or

my ($directory) = $fullpath =~ m|^(?:(.*)/)?|;
[download]

if you don't like the trailing slash on the path...