pFor = withAnnotation $ do
  reserved "for"
  var <- identifier
  reserved ":="
  start <- pExpression
  reserved "to"
  end <- pExpression
  reserved "do"
  sts <- pBlock
  return $ For var start end sts
pFor = withAnnotation $ do
  reserved "for"
  var <- identifier
  reserved ":="
  start <- pExpression
  reserved "to"
  end <- pExpression
  reserved "do"
  sts <- pBlock
  return $ For var start end sts
pFor = withAnnotation $ do
  reserved "for"
  var <- identifier
  reserved ":="
  start <- pExpression
  reserved "to"
  end <- pExpression
  reserved "do"
  sts <- pBlock
  return $ For var start end sts