text <- "categories: crime, punishment, france\nTags: valjean, javert,les mis\nAt the end of the day, the criminal Valjean escaped once more."
sub("(?n)^categor(?:.*\n){2}", "", text)
sub("^categor(?:.*\n){2}", "", text, perl=TRUE)
dGV4dCA8LSAiY2F0ZWdvcmllczogY3JpbWUsIHB1bmlzaG1lbnQsIGZyYW5jZVxuVGFnczogdmFsamVhbiwgamF2ZXJ0LGxlcyBtaXNcbkF0IHRoZSBlbmQgb2YgdGhlIGRheSwgdGhlIGNyaW1pbmFsIFZhbGplYW4gZXNjYXBlZCBvbmNlIG1vcmUuIgpzdWIoIig/bileY2F0ZWdvcig/Oi4qXG4pezJ9IiwgIiIsIHRleHQpCnN1YigiXmNhdGVnb3IoPzouKlxuKXsyfSIsICIiLCB0ZXh0LCBwZXJsPVRSVUUp