=over

=item sqrt EXPR
X<sqrt> X<root> X<square root>

=item sqrt

Return the positive square root of EXPR.  If EXPR is omitted, uses
L<C<$_>|perlvar/$_>.  Works only for non-negative operands unless you've
loaded the L<C<Math::Complex>|Math::Complex> module.

    use Math::Complex;
    print sqrt(-4);    # prints 2i

=back