bah,valueA
foo,valueB
foo,valueC
bar,valueD
[download]

results in

bah,valueA
bar,valueD
foo,valueB,valueC
[download]

and not

bah,valueA
foo,valueB,valueC
bar,valueD
[download]

Therefore, merlyn assumes they are sorted (or assumes the order of the lines in the result doesn't matter, but then why call sort?).