I had made the assumption that the files were being stored in an array. I hadn't thought of any other way to get the file list from the directory outside of File::Find which creates an array.

I really overdid counting the instances of each file extension. I had thought of incrementation, but I hadn't thought to use it to define a previously undefined variable. So, the code below is better without the constant my $num = 1;.

my %extensions;
for my $file (sort @files) {
  my @split = split(/\./,$file);
  my $key = $split[1];
  ++$extensions{$key};
}
while (my ($key,$value) = each %extensions) {
  print $key." - ".$value."\n";
}
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