Verification Exception with Custom JS Function

Hi, I have been receiving this runtime error, "VerificationException: Error verifying MainScript:GetOperatorParam (object): Unexpected object for ldvirtftn at 0x0032 MainScript.OnGUI () (at Assets/MainScript.js:88)"

GetOperatorParam(str) is a custom function I made:

 function GetOperatorParam(string)
 {
     var str = string.ToString();
     var Param1 = "";
     var Param2 = "";
     var Operator = "";
     var IsParam2 = false;
     for(var count = 0; count < str.Length; count++)
     {
         if(str[count].ToString == "*" || str[count].ToString == "+" || str[count].ToString == "/" || str[count].ToString == "-" || str[count].ToString == "="
             || str[count].ToString == "^")
         {
             IsParam2 = true;
             Operator = str[count].ToString();
             count++;
         }
         
         if(!IsParam2)
         {
             if(str[count].ToString() != " ")
                 Param1 += str[count].ToString();
         }
         else
         {
             if(str[count].ToString() != " ")
                 Param2 += str[count].ToString();
         }
     }
     return new OperatorParam(Param1, Param2, Operator);
 }

and this part of my script uses it:

 else if (Level == 2)
         {
             var TempOpParam : OperatorParam;
             for(var count = 0; count < Lines.length; count++)
             {
                 TempOpParam = GetOperatorParam(Lines[count].ToString());
                 Debug.Log(TempOpParam.ToString());
                 if(TempOpParam.Param1 == "Cam.Position")
                 {
                     if(TempOpParam.Operator == "=")
                     {
                         if(GetArray(GetBraceGroup(TempOpParam.Param2)).length != 3)
                         {
                             LoggerOn = true;
                             GUIOn = false;
                             LoggerText += "Error!! Invalid number of arguments when attempting to set Cam.Position.";
                         }
                     }
                 }
             }
         }

Why can't GetOperatorParam() get verified, and what is verification?