Katy Perry. (Photo: AP) Los Angeles - Katy Perry shared a cryptic tweet after becoming embroiled in Calvin Harris' rant towards Taylor Swift on Twitter. Taylor's representative confirmed on Wednesday that she had penned his new tune, telling MailOnline: "Taylor Swift wrote This Is What You Came For under the pseudonym Nils Sjöberg." Nils is a Swedish artist who runs a Tumblr account called Nils First World Problems, in which people can submit their first world problems to him and he then translates them into his drawings.