# sqrt - perldoc - phpman

    sqrt EXPR
    sqrt    Return the positive square root of EXPR. If EXPR is omitted,
            uses $_. Works only for non-negative operands unless you've
            loaded the "[Math::Complex](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3AComplex/markdown)" module.

                use [Math::Complex](https://www.chedong.com/phpMan.php/perldoc/Math%3A%3AComplex/markdown);
                print sqrt(-4);    # prints 2i