^ is a binary or bit wise operator:
http://www.w3resource.com/javascript/operators/bitwise-operator.php

For x powered by y, use Math.pow(x,y) instead:
http://www.w3schools.com/jsref/jsref_pow.asp

BTW: pow(x,y) also works. Also available in the global scope: abs, sin, cos, tan, ceil, floor, max, min, sqrt, log, PI, ...

I write "pow(4,2)". Qcad says "pow(4.2) is not a normal number".
I wrote "comma" and Qcad says "point"?!
Is it something to do locales? We use here comma as a decimal point.

Unfortunately, if you use a comma as decimal point, this will not work since the expression would be ambiguous.
f(1,2,3) could mean call f with three parameters 1, 2 and 3 or two parameters 1.2 and 3 or two parameters 1 and 2.3.

You can force QCAD to work with a dot as decimal point instead under:
Edit > Application Preferences > General > Coordinate Format