Your variables are declared with my within the while loop. So they are re-initialized on each run and shouldn't know of their previous value.

And you assign a value to $url on each run; so it should even work without the my inside the loop, as the content of $url is overwritten on each run of the loop.

Ergo: If you see the same output per run, the problem is in FetchURL as others already mentioned.

$ perl -wle '
> my $i = 1;
> while ( $i < 5 ) {
>   my $j = $i++;
>   print $j;
> }'
1
2
3
4
$
[download]

$ perl -wle '
my $i = 1;
my $j;
while ( $i < 5 ) {
  $j = $i++;
  print $j;
}'
1
2
3
4
$
[download]

You can see, each print prints the value of $i and $j doesn't "remember" its previous content.