Documentation for prefix (C-like) form assembled from the following pages:

Class: Signature §

From Signature

(Signature) prefix (C-like) form §

This is similar to placing type constraints on variables like my Type $var = 20;, except the $var is a definition for a routine.

my Int sub bar { 1 };     # Valid 

my 42 sub bad-answer {};  # This will fail.