The children are learning the poem by heart.
The children have learnt the poem by heart.
The children have learnt this poem by heart.
The children learnt the poem by heart.
Ann, don't eat too much ice-cream. What isn't she doing? What hasn't she done? Who hasn't eaten too much ice-cream? What didn't she do?
Ann is not eating ice-cream.
Ann has not eaten too much ice-cream.
Ann has not eaten too much ice-cream.
Ann did not eat too much ice-cream.