11A. quoting and scope
----------------------
Quoted expressions start with a backquote. The value of a quoted
expression is not the result from the computation of the expression,
but the address of the code. This result may then be passed on as
a normal variable, or as an argument to certain functions.
example:

myfunc:=`x*x*x

myfunc is now a pointer to a `function' that computes x^3 when evaluated.
These pointers to functions are very different from normal PROCs, and
you should never mix the two up. The biggest differences are that a
quoted expression is just a simple expression, and thus cannot have its
own local variables. In our example, "x" is just a local or global variable.
That's where we have to be cautious:
if we evaluate myfunc somewhat later in the same PROC, x may be local,
but if myfunc is given as parameter to another PROC, and then evaluated,
x needs of course to be global. There's no scope checking on this.