Variadic function

If a subroutine has no formal parameters but mentions the variables @_ or %_ in its body, it will accept arbitrary positional or keyword arguments, respectively. You can even use both in the same function.

sub foo {
   .say for @_;
   say .key, ': ', .value for %_;
}

foo 1, 2, command => 'buckle my shoe',
    3, 4, order => 'knock at the door';

This prints:

1
2
3
4
command: buckle my shoe
order: knock at the door

Raku also supports slurpy arrays and hashes, which are formal parameters that consume extra positional and keyword arguments like @_ and %_. You can make a parameter slurpy with the * twigil. This implementation of &foo works just like the last:

sub foo (*@positional, *%named) {
   .say for @positional;
   say .key, ': ', .value for %named;
}

Unlike in Perl 5, arrays and hashes aren't flattened automatically. Use the | operator to flatten:

foo |@ary, |%hsh;