while (cond1) {
  if (cond2) {
    statement;
    if (cond3) {
      statement;
      statement;
      for (range) {
        something;
        something;
        something;
      }
    }
  }
  else {
    last;
  }
}

##</code><code>##

while (cond1) {
  last unless (cond2);
  statement
  next unless (cond3);
  statement
  statement
  for (range) {
    something
    something
    something
  }
}