I don't see where you assume that; AFAICT your solution will work whether or not that's true. Perhaps you are just pointing out that the operation will not be reversable if there are existing commas?
Implicitly, you are also assuming that records should be merged regardless of their position in the file; it's possible that only adjacent records should be candidates for merging.

In reply to Re^2: amalgamate similar lines by ysth
in thread amalgamate similar lines by Anonymous Monk

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