Also need something to prevent recursion (file1 includes file2 includes file1), for example:

package Include;

...

my $sanity_count = 0;

sub import 
{
    my (undef, @files) = @_;
    
    @files = find_files(@files);    # cdarke added
        
    $sanity_count?croak ("Possible recursion!: @files"):$sanity_count+
++;

    ...
[download]

This also protects against use Include $0;