1. A computer-implemented method for assisting a user of a content item, comprising: receiving, by a search expression generator operated by a computer system, the content item, wherein the content item is a selected one of a web page, a post to a social networking site, a post to a blog, a post to an online bulletin board, a document, or an electronic message, having text divisible into a plurality of subtexts; and generating a search expression, by the search expression generator, based on the content item, to search other content items, through execution of the search expression, wherein the search expression is to include a hierarchy of a plurality of nested juxtaposition sub-expressions corresponding with nesting of subtexts of the content item; wherein the search expression is to be applied by a search engine operated on the same or a different computer system, to the other content items to generate a search result; wherein generating comprises recursively dividing the text of the content item into the subtexts, and transforming the subtexts into the search sub-expressions; and wherein the content item is a first content item, and the search result includes a second content item to be recommended to the user.