JavaScript example:

=begin code :lang<js>
export function add(x, y = 0) {
  return x + y;
}
=end code

Rendered JavaScript example:

export function add(x, y = 0) {
  return x + y;
}

Python example:

=begin code :lang<python>
def fib(n):    # write Fibonacci series up to n
    """Print a Fibonacci series up to n."""
    a, b = 0, 1
    while a < n:
        print(a, end=' ')
        a, b = b, a+b
    print()
# Now call the function we just defined:
fib(2000)
=end code

Rendered Python example:

def fib(n):    # write Fibonacci series up to n
    """Print a Fibonacci series up to n."""
    a, b = 0, 1
    while a < n:
        print(a, end=' ')
        a, b = b, a+b
    print()
# Now call the function we just defined:
fib(2000)

Ruby example:

=begin code :lang<ruby>
class Person
  def initialize(name)
    @name = name
  end

  def greet
    puts "Hello, I'm #{@name}!"
  end
end

person = Person.new("Alice")
person.greet
=end code

Rendered Ruby example:

class Person
  def initialize(name)
    @name = name
  end

  def greet
    puts "Hello, I'm #{@name}!"
  end
end

person = Person.new("Alice")
person.greet

Perl example:

=begin code :lang<perl>
package Calculator;

sub new {
    my $class = shift;
    return bless {}, $class;
}

sub add {
    my ($self, $x, $y) = @_;
    return $x + $y;
}

my $calc = Calculator->new();
print $calc->add(5, 3) . "\n";
=end code

Rendered Perl example:

package Calculator;

sub new {
    my $class = shift;
    return bless {}, $class;
}

sub add {
    my ($self, $x, $y) = @_;
    return $x + $y;
}

my $calc = Calculator->new();
print $calc->add(5, 3) . "\n";

Raku example:

=begin code :lang<raku>
sub greet($name) {
    say "Hello, $name!";
}
=end code

Rendered Raku example:

sub greet($name) {
    say "Hello, $name!";
}