Quadratic equation in Perl

Example for versions perl 5.12.1, perl 5.8.8

Note that Perl 6 has no backwards compatibility; this example won’t be valid in Perl 6. 

$A = <>;
if ($A == 0) {
    print "Not a quadratic equation.";
}
else {
    $B = <>;
    $C = <>;
    $D = $B * $B - 4 * $A * $C;
    if ($D == 0) {
        print "x = ", -0.5 * $B / $A;
    }
    else {
        if ($D > 0) {
            print "x1 = ", 0.5*(-$B + sqrt($D))/$A, "\nx2 = ", 0.5*(-$B - sqrt($D))/$A
        }
        else {
            print "x1 = (", -0.5*$B/$A, ",", 0.5*sqrt(-$D)/$A, ")\nx2 = (", -0.5*$B/$A, ",", -0.5*sqrt(-$D)/$A, ")\n"
        }
    }
}