Organise the code like this:

File main.pl:

#! perl
use strict;
use warnings;
use MyModule;
use YourModule;
# ... as before ...
[download]

File SuperModule.pm:

#! perl
package SuperModule;
# ... as before ...
1;
[download]

File MyModule.pm:

#! perl
package MyModule;
use strict;
use warnings;
use SuperModule;
our @ISA = qw( SuperModule );
# ... as before ...
1;
[download]

File YourModule.pm:

#! perl
package YourModule;
use strict;
use warnings;
use SuperModule;
our @ISA = qw( SuperModule );
# ... as before ...
1;
[download]

Note that a standalone module (i.e., a file with a .pm extension) must return true on success. Hence the common practice of ending each module with 1; on a line by itself. See Perl Modules in perlmod.

This scheme assumes that the four files are in the same directory. If they’re not, you will need to investigate the use lib pragma. See lib.

Hope that helps,