I need to compare two files. These files have a key and a value on each line. I need to note when a key is in one file, and not in the other. I also need to note when the keys match, but the values are different. ex. given: 
left-file   right-file
1,a         1,a
2,b         3,c
4,f         4,g
5,h         5,h

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I need 2 absent from right-file, 3 absent from left-file and 4 is different. diff works so long as difference are separated by one or mores lines with a matching key and value. With the above input files diff produces: 
< 2,b
< 4,f
---
> 3,c
> 4,g

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Which is not quite right. -Bass has the beginnings of the shell of what I need. Being lazy, I was hoping the CPAN would have the algorithm I need, but I have found nothing. Note that the files are big, 1/2 million lines or so and the key and value are actually multiple fields.

In reply to File comparison: not diff by rschuler

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