What is the effect of the words- 'alas' and 'ah me' in the poem sympathy by Paul Lawrence Dunbar?

Paul Lawrence Dunbar uses the phrase 'alas' in the line 'I know what the caged bird feels, alas', to indicate that the feeling that he can relate to is not a positive feeling. 'Ah me' is used in the line 'I know why the caged bird sings, ah me' to indicate that the poet can relate to the bird's plight. He can only understand the pain and suffering of the bird.

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