sub hash 
{
    my %in = @_;
    . . . 
}

sub hashref 
{
    my $in = shift;
    my %in = %{ $in };
    . . . 
}

hash( foo => 'bar' );
hashref({ foo => 'bar' });

##</code><code>##

sub hashref_and_positional 
{
    my $param1 = shift;
    my $param2 = shift;
    my $in     = shift;
    my %in     = %{ $in };

    . . . 
}

hashref_and_positional('foo', 'bar', { baz => 'blah' });