CallSub.BAS -- Test BASIC Call and Sub Statements                               
The next printed line should be from the Subroutine.                            
                                                                                
This is written from the Subroutine.                                            
The value of variable <xarg> is 5                                               
The value of variable <yarg$> is Hello                                          
The value of variable <tvar> is  17                                             
The value of variable <tvar> is reset to  99                                    
                                                                                
This is back at the main program.                                               
The value of variable <testvar> is now  17                                      
Did it work?                                                                    
