Five lines, barely twenty words, and a question most people have asked themselves in some form late at night. The speaker says "Tell me" and asks what they ought to regret: the person they are, or the person they are not. It sounds like a request for advice, but it works more like a room with two doors that open onto the same corridor.
The grammar of the central question matters. The speaker does not ask "Do I regret anything?" Regret is taken for granted, and only its object is left open. "What should I regret" treats regret as a bill that will certainly arrive, with the speaker wondering which account to charge it to. The word "should" adds to this. Regret is normally a feeling that happens to us, but here it becomes a duty that can be done correctly or incorrectly. Judging by that phrasing, the speaker seems to have absorbed the idea that some regret is expected of them, and now wants to know which kind.
The two options mirror each other almost exactly. "Who I am" and "What I am not" share the same small words and the same "I am" at the centre, and only the "not" turns one into its opposite. The shift from "who" to "what" is subtler. "Who" belongs to a person. "What" is colder, closer to an inventory of missing things: qualities, achievements, possibilities. So the existing self gets a human pronoun, while the unlived self is reduced to a list of unmet standards. The poem never says this outright, but the choice of words suggests that the self we compare ourselves to is less a person than a pile of absences.
Then there is the line that consists only of "Or". It is the shortest line in the poem, a single syllable, and it works as a hinge. The question mark has already come after "Who I am?", so the speaker has finished asking and then circles back, as if the first question were not enough. That gives the poem a restless, second-guessing movement, a mind that cannot leave a thought alone.
The punctuation at the end of line two is just as odd. Instead of a question mark, the line ends in a tilde, a small wave. As printed here, it looks like a trailing-off, neither a full stop nor a proper question, the sound of a voice that hasn't decided whether it is asking or sighing. Whether or not it was deliberate, it fits the wavering tone.
The sound of the poem is stripped back. There is no rhyme and no regular metre, only free verse in lines of three, five, three, one and four syllables. Nearly every word is a single syllable. The one exception is "regret", the title word, which stands out like a stone in a bare field. The poem also contains no images at all: no objects, no landscape, no colour. This leaves the speaker nothing concrete to hide behind, and the white space around the words starts to feel like part of the subject, an empty place shaped like the self that isn't there. The final word, "not", ends the poem on a hard negative, with no answer and no softening afterwards.
What gives the poem its force is the trap inside the question. Neither regret can do anything. No one can stop being who they are, and no one becomes what they are not by wishing it. Placed side by side, the two options make regret look useless in both directions. A reader might hear despair in that, or a dry, almost playful argument: if every answer leads to regret, perhaps regret is a poor guide to begin with. The poem never decides between these readings.
That openness is also why it suits a classroom. Its few words ask the reader to supply the rest, whether that is comparing yourself to other people, to an earlier version of yourself, or to what you were told you would become. And since "Tell me" has no named listener, the question ends up addressed to whoever is reading.