You can't use slashes in the name of the required file. You can use either double colons, and no file extension (".pm" is assumed), or you can use a string (a quoted literal or a variable) with a path with slashes and with file extension. So you can do

require "/a/b/script";
[download]

if it has no file extension, or

require "/a/b/script.pl";
[download]

if it has ".pl" as file extension.