Question: how many perfect games have there been in major league history
[{'answer': '23 official perfect games', 'provenance': [{'wikipedia_id': '33940138', 'title': 'List of Major League Baseball perfect games', 'start_paragraph_id': 1, 'start_character': 100, 'end_paragraph_id': 1, 'end_character': 125, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '33940138', 'title': 'List of Major League Baseball perfect games', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 950, 'bleu_score': 0.945776014351493, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11484537400211650549}, 'section': 'Section::::Abstract.'}]}]