Poem and parody -- isomorphic?

In mathematics, algebraic systems that have different objects but the same structure are described as isomorphic.  The parody in poetry illustrates the same idea -- a new poem is created that matches the form of a chosen poem, but uses different words.  For example, here are the opening stanzas of a poem published in 1799 by Robert Southey (1777-1843) that was later parodied by Lewis Carroll (1832-1898) in Alice's Adventures in Wonderland.