I know this is a Perl-forum but there is a very quick way to do this with uniq.

If the formats are exactly the same, you could use:

cat file1 file2 | uniq -u

to extract all lines that do not occur twice, i.e. when (tableA eq tableB && columnA eq columnB) fails.

All lines that do occur twice can be extracted with:

cat file1 file2 | uniq -d

If you're files differ in format like the use of spaces or something, consider using a filter

Note that this gives you no indication whether only the columns, or the tables or both didn't match. For that you have to user perl after all, I guess