Apart from the hint given in Re: Scripts work when run individually but not when run as one compiled script by GotToBTru - three points:

1. You mix path delimiters.
   

   sub csv_xlsx{
       my $dir = "C:\\Temp\\Data";
       foreach my $fp (glob("$dir/*.csv")) {
          ...
       }
       unlink glob "C:\\Temp\\Data\\*.csv" or warn $! ;
   }
   [download]

   To avoid that, always use File::Spec for path operations.
2. Did you check what those glob() expressions do return?
3. What are you doing with @class_files ?

And a last hint - to format your indenting before posting, you can use Perl::Tidy, which expands tabs and sets the shift width to 4 spaces, given the proper rules for that. ;-)