Index is Less Than Zero + Flawed Code

Can you tell me what is wrong with my code? Essentially, I am trying to loop through a tab seperated file which I load and then create prefabs when it reaches a certain character. I have not gotten to the prefab code yet, as I am simply trying to properly loop through this multidimensional array.

The code is here:

 import System.IO;
 
 var ddata_b = new Array();
 var ddata = new Array();
 
 function Start () {
      try {
         var sr = new File.OpenText("Assets\\dungeon.txt");
 
  
 
     var input = "";
     var i = 0 ;
     while (true) {
 
         input = sr.ReadLine();
 
         if (input == null) { break; }
 
         ddata_b[i] = input;
         i++;
     }
     sr.Close();
 
  } catch (e) {
         // Let the user know what went wrong.
         print("The file could not be read:");
         print(e.Message);
     }
     
     //done grabbing data
     var i2 = 0;
       while(ddata_b.length >= i2) {
       ddata[i2] = ddata_b[i2].ToString().Split("    "[0]);
       i2++;
     }
 }
 
 populate(ddata);
 
 function Update () {
 
 }
 
 function populate(inp) {
     var x=0;
     var z=0;
     while(inp.length >= x) {
         Debug.Log("This is being run...");
         while(inp[x].length >= z) {
         if(inp[x][z]=="F") Debug.Log("Floor tile at: " + x + z);
         z++;
         }
         z=0;
         x++;
         Debug.Log("New Line.");
     }
     Debug.Log("Done.");
 }

I am getting the ArgumentOutOfRangeExceptions (Index is Less Than Zero or more than or equal to the lsit count) errors at these lines:

         while(inp[x].length >= z) {

and

       ddata[i2] = ddata_b[i2].ToString().Split("    "[0]);

Thanks guys!