That should work, but consider:

$j = 23;
$i = $j;
LOOP:
while (1) {
   if ($index[$i] eq 'blah') {
      last LOOP;
   } elsif ($i == $#array) {
      $i = 0;
   } else {
      $i++;
   }
)
[download]

Update: added missing closing quote.

Second update: per wog noted that you actually "start over" at 1, because next performs the $i++. However, I think you want to start at the beginning of the array, right? If not, change the code to:

$j = 23;
$i = $j;
LOOP:
while (1) {
   if ($index[$i] eq 'blah') {
      last LOOP;
   } elsif ($i == $#array) {
      $i = 0;
   }
   $i++;
)
[download]