sub MAIN ( $num1, #= Number to perform arithmatic on $num2 #= Second number to perform arithmatic on ) { die "unexpected input" unless is-numeric($num1) and is-numeric($num2); say "sum is {$num1 + $num2}"; say "difference is {$num1 - $num2}"; say "product is {$num1 * $num2}"; say "quotient is {$num1 / $num2}"; } sub is-numeric ($num) { return val($num) ~~ Numeric; }