Started into the Expression and Operand obejcts.

__set.cpp

@@ -22,7 +22,7 @@ namespace jet {
 	 if(variableDefined("expr")) {
 	    if(variableDefined("eval"))
 	      throw coreutils::Exception("Cannot use eval with expr.");
-	    global.variables[variables["name"]] = Expression(variables["expr"]);	    
+	    global.variables[variables["name"]] = Expression(variables["expr"]).string;	    
 	 } else if(hasContainer) {
 	    if(evaluate) {
 	       global.variables[variables["name"]] = out;