Or another solution with Schwartzian Transform: I can just give you a list of sorted keys:

my @sortedKeys =
  map  { $_->[0] }
  sort { $a->[1] <=> $b->[1] }
  map  { [
          $_, 
          join("", # xx.XXX.xx.X => xxxXXXxxxXXX
               map { sprintf("%03d", $_) }
               ( /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/ )
          )
         ]
       }
  keys %hash;
[download]

But this solution might not be the fastest one :-)