What am I missing?

Perhaps it's just the way that the particular perl has been configured.
Try running the following script (using the perl that's giving you the problem):

use strict;
use warnings;
use Config;

for(keys(%Config)) {
  print "$_ : $Config{$_}\n"
   if $_ =~ /install/i;
}
[download]

That should give you a listing of where perl wants various things to be installed. (Don't be worried if some of the keys are unset.)

Cheers,
Rob