📘 Subroutines, or subs in Raku

For a sub, which takes no arguments, its definition and the call are very straightforward and easy.

sub call-me {
    say "I'm called"
}

call-me;

The syntax for declaring a sub’s parameters is similar to what other languages (including Perl 5.20 and higher) provide.

sub cube($x) {
    return $x ** 3;
}

say cube(3); # 27

The required parameters are a comma-separated list in the parentheses immediately after the sub name. No other keywords, such as my, are required to declare them.

sub min($x, $y) {
    return $x < $y ?? $x !! $y;
}

say min(-2, 2);  # -2
say min(42, 24); # 24

(?? … !! is a ternary operator in Perl 6. Also, there’s a built-in operator min; see the details in the Chapter 2.)

The above-declared arguments are required; thus, if a sub is called with a different number of actual arguments, an error will occur.