use List::Util qw( sum );
use List::MoreUtils qw( pairwise );

sub distance
{
    my( $aa, $bb ) = @_;
    $aa == $bb and return 0; # optimiz.
    @$aa == @$bb or die "coordinate vectors unequal length!";
    sqrt sum pairwise { ( $a - $b ) ** 2 } @$aa, @$bb 
}
[download]