Those poems are called palindromic poems. They can be read the same way forward as backward, resulting in different meanings each way.
A Palindrome is a word or phrase that reads the same backwards as forwards. Things like Napoleon's comment 'Able was I ere I saw Elba.', or first words in the Garden of Eden 'Madam I'm Adam.' A good collection of pallindromes is Weird Al Yankovic's song Bob (Bob is one, as is Otto) Which should be available on video sites such as You tube.