Final answer:
Perry's reaction to the letter written by Don Cullivan reflects his perspective on the limitations of the Missouri Compromise line.
Step-by-step explanation:
Perry's reaction to the letter written by Don Cullivan is significant because it reflects his perspective on the Missouri Compromise line and its limitations. When Perry states that the line is "a reprieve only, not a final sentence," he means that the compromise is only a temporary solution to the issue of slavery and does not address the underlying tensions between the North and the South. Perry's reaction suggests that he recognizes the need for a more comprehensive resolution to the problem of slavery.