I am more interested in writing poems that are ideas for poems,and that could have come out differently. Some are variations on a theme, or a them without variations. In some cases, I begin the poem and include instructions for the reader to finish it: "repeat, with variations." The poem should have its implicit set of rules of instructions, or these can be implicit. Either way works.
So the instructions might say: start with a poem you remember the beginning of, write that down, then once you start forgetting, fill in your own substitute lines.