Non-nursery rhyme

Mary had a little lamb
But the lamb was mean to Mary.
Mary tried to get rid of it,
But it refused to leave.
Mary tried a trick or two
yet it did not comply.
Days went by and nights went by
But the lamb stayed on for long.
Mary wished to kill the lamb
But too bad it was already dead.

So Mary, Mary be careful,
Next time you have a lamb.