$x = Dog->new(
   -size          => 'small',   # ok, this would be
   -aggresiveness => 'low',     # quoted by =>, and
   -hair_style    => 'curly',   # ...
   -hair_lenght   => 'short',
)

package Dog;
sub new {
   my %args = @_;
   my $size = $args{-size};     # ... these would be
   my $age  = $args{-age};      # quoted by the {}, but ...
   my %hair_properties = @args{
     -hair_style,               # ... these would need
     -hair_lenght,              # quoting without
     -hair_colour,              # unary-'-'.
   };
   ...
}