I don't have Win32, so I can't get shortpath, but I suspect it's because you chdir, and that path to file is no longer there.

Also, when you create_file() you should check the open

sub create_file{
open (MYFILE, ">$output_directory/token.txt") or die "$!\n";
print MYFILE "ciao";
close (MYFILE); 
}
[download]

I get "no such file or directory". It would also help if you made a self-contained fully running example.