my @keys = keys %{$database[0]};  #optionally use sort keys
my $pdl1 = pdl (@{$database[0]}{@keys});
my $n1 = norm $pdl1;
my ($pdl2, $n2, $dotproduct, $d, @angles);
for (0..$3database) {
      $pdl2 = pdl ((@{$database[$_]}{@keys});
      $n2 = norm $pdl2;
      $dotproduct = inner ($n1, $n2);
      $d = dotproduct->sclr();
      $angles[$_] = (180/3.1415926)*acos($d);
}