You are looping over an array you are adding to, so you are never reaching the end.

This is somewhat similar to the following loop

my $i=1; my $end= 2;
while ($i++<$end) {
  $end++;
}
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Note that

y @a = (1);
foreach (sort @a) { push @a, 1; }
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stops immediately, because here you are looping over the anonymous array that is not expanding.