+ is the unary plus operator, which casts its operand to the numerical context. The action is equivalent to the call of the Numeric method.
my Str $price = '4' ~ '2'; my Int $amount = +$price; say $amount; # 42 say $price.Numeric; # 42
We will see one of the important use cases of the unary plus in Chapter 6: +$/. That construction converts an object of the Match class that contains information about the matched part of the regular expression into a number.