run  -- Command or operation, one input.
     The input must be a list, containing a  Logo  instruction  line.   The
     list is run as if you typed it directly to Logo.  Example:

     to while :condition :cmd
     if not run :condition [stop]
     run :cmd
     while :condition :cmd
     end

     make "number 1
     while [:number < 5] [print :number; make "number :number+1]

     The run procedure can be used as an operation, if its input is a  Logo
     expression which produces a value, instead of a complete instruction:

     print run [sum 2 3]
