The fact that Simon uses repetition in the chorus helps to bring out the idea that there is always human freedom to extricate oneself from challenging situations.  The chorus brings this home through repetition and rhyme, almost as if there is a design deliberate in breaking free from commitments.  The rhyme is so strong in terms of linking name to method of leaving ("Bus" and "Gus," "Key" and "Lee," and "Back" and "Jack.")   This is fairly powerful in its scope.  Whereas most poems spend time explaining how human beings are meant to be with one another, Simon goes to another extreme.  The rhyme brings this home, almost to suggest that it is natural and part of the natural design to separate and leave.  Simon is one who stresses that individuals are able to break free and "walk out," using repetition and rhyme as part of this process.  The imagery, mental pictures, created of a man asking his mistress, who is depicted as all knowing, how to get out of a situation helps to feed this idea.  The notion of "It grieves me so to see you in such pain," is another image that plays off of the chorus' repetition of how to escape such challenges.