Range violation

[Vino via Digitalmars-d-learn]

Hi All,

   Request your help on the below program, when I execute the 
program without passing any arguments it is throwing Range 
violation errors

Error:
core.exception.RangeError@test.d(21): Range violation
----------------
0x004068CC
0x00408CF3
0x00408CB7
0x00408BB8
0x0040558F
0x74FE336A in BaseThreadInitThunk
0x770F98F2 in RtlInitializeExceptionChain
0x770F98C5 in RtlInitializeExceptionChain

Program:
import std.stdio;
import std.getopt;
import std.path;
import core.stdc.stdlib: exit;

void Test1() {
writeln("This is Test1");
}
void Test2() {
writeln("This is Test2");
}
void Test3() {
writeln("This is Help");
}

void main (string[] args) {
if (args.length < 1 || args.length > 2) {
        writeln(args[0].baseName, ":No Arguments Provided");
        exit(-1);
                }

string op = args[1];
getopt(args, std.getopt.config.caseInsensitive, 
std.getopt.config.stopOnFirstNonOption);

switch (op) {
case "dryrun" , "run" :
        Test1;
        Test2;
break;
case "help" :
        Test3;
        break;
default :
                 writefln("Unknown operation");
         }
}

From,
Vino.B