my $pdispatch = {
	'+' => sub { $_[0] + $_[1] },
	'-' => sub { $_[0] - $_[1] },
	'*' => sub { $_[0] * $_[1] },
	'/' => sub { $_[0] / $_[1] },
};

# and later ...
my $operator = qw(+ - * /)[int rand 4];
my $true_answer = $pdispatch->{$operator}->($value1, $value2);