So, using File::Spec the following would need to be altered.

my %files;
for my $raw_file (@file_list) {
  my @file_parts = split(/\//,$raw_file);
  my $file = pop @file_parts;
  my $file_size = -s $raw_file;
  push @{$files{"$file ($file_size bytes)"}}, $raw_file;
}
[download]

The following is the alteration.

my %files;
for my $raw_file (@file_list) {
  my ($volume,$directories,$file) = File::Spec->splitpath($raw_file);
  my $file_size = -s $raw_file;
  push @{$files{"$file ($file_size bytes)"}}, $raw_file;
}
[download]

So, no more spliting and popping for the file name. Thanks for the tip!