grammar Exp {
	token TOP { ^ <exp(2)> $ }
	multi rule exp(0) { \d | ['(' <exp(2)>')'] }
	multi rule exp($pred) { <exp($pred-1)> +% <op($pred)>}

# Ordered from loosest to tightest: should descend into
# tighter operators first
	multi token op(2) { '+' | '-'}
	multi token op(1) { '*' | '/'}
}

class ParseExp {
	method TOP($/) {
		make $<exp>.made;
	}
	method exp($/) {
		unless $<exp> {
			make $/;
			return;
		}
		unless $<exp>.elems > 1 {
			if $<exp>[0] {
				make $<exp>[0].made;
			} else {
				make $<exp>.made;
			}
			return;
		}
		given $<op>[0].Str {
			when "+" {
				make [+] $<exp>.map(*.made);
			}
			when "-" {
				make [-] $<exp>.map(*.made);
			}
			when "*" {
				make [*] $<exp>.map(*.made);
			}
			when "/" {
				make [/] $<exp>.map(*.made);
			}
		}
	}
}

sub MAIN($str) {
	say Exp.parse($str, actions => ParseExp.new).made;
}