my ($zahl1, $zahl2, $operator) = (7, 3, '*');

my %switch = (
    '*' => sub { return $_[0] * $_[1] },
    '/' => sub { return $_[0] / $_[1] },
    '+' => sub { return $_[0] + $_[1] },
    '-' => sub { return $_[0] - $_[1] },
);
    
my $ergebnis = $switch{$operator}->($zahl1, $zahl2);