sub new {
   my $class = shift;
   my %self = %{$_[0]} if ref $_[0];
   ...
}

##</code><code>##

# Class->new();
# Class->new({ k=>v, ... });
sub new {
   my $class = shift;
   my %self = ref $_[0] ? %{$_[0]} : ();
   ...

##</code><code>##

# Class->new();
# Class->new({ k=>v, ... });
# Class->new( k=>v, ... );
sub new {
   my $class = shift;
   my %self = ref $_[0] ? %{$_[0]} : @_;
   ...
}

##</code><code>##

# Class->new();
# Class->new( k=>v, ... );
sub new {
   my ($class, %self) = @_;
   ...
}