This example demonstrates how to preserve only the last N occurrences of lines matching a keyword while searching through a document, yielding each matching line along with the saved history. The code uses Python’s `collections.deque` with a `maxlen` parameter to automatically drop the oldest entries once the buffer exceeds the specified size. A generator function `search` iterates over the input lines, checks for the keyword pattern, and yields both the current match and the deque containing previous matches. The example input `['abc', 'bcd', 'hahaha', 'acd', 'cef']` is processed with a history limit of 3, producing a final deque showing only the last three matched lines.