Example of Substring Operations

   string strA = "123456789";
   strB = strA.substr(2,3);              // value is "345"
   strC = strA.substr(2);                // value is "3456789"

   string strD = "123456789";
   strD.erase(3,5);                      // value is "1239"
   strD.erase(2);                        // value is "12"
   strD.erase();                         // value is ""

   string strE = "12345";
   string in = "abcde";
   strE.insert(2,in);                    // value is "12abcde345"
   strE = "12345";
   strE.insert(3,in,1,3);                // value is "123bcd45"
   strE = "12345";
   strE.insert(2,"UVWXYZ",3);            // value is "12UVW345"
   strE = "12345";
   strE.insert(4,"Boo");                 // value is "1234Boo5"
   strE = "12345";
   strE.insert(1,3,'x');                 // value is "1xxx2345"

   strE = "12345";
   in = "abcde";
   strE.replace(1,2,in);                 // value is "1abcde45"
   strE = "12345";
   strE.replace(1,2,in,3,2);             // value is "1de45"
   strE = "12345";
   strE.replace(1,2,"stuv",2);           // value is "1st45"
   strE = "12345";
   strE.replace(1,2,"stuv");             // value is "1stuv45"
   strE = "12345";
   strE.replace(1,2,3,'B');              // value is "1BBB45"