** Using WeBWorK **

There is a slightly easier way of selecting the variable name: list_random. This function returns one of its arguments chosen at random. So

    $var = list_random('w','x','y','z');

would select the variable name at random, and could replace your three-line version of doing this.

[Of course, you could have done your version in only one line as well,

    $var = ('w','x','y','z')[random(0,3,1)];

but list_random is slightly cleaner, as you don't have to worry about knowing the number of elements in the array.]