I guess my question is "But why???". This doesn't seem to serve any useful purpose, does it? For instance, if you change the script to read

It's used mostly for unordered function parameters:

$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-'-'.
   };
   ...
}
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