Try adding use diagnostics; at the top of your program to get explanations of the messages. In this case it's just a warning, not an error, and since you seem to be running your code with different input files than the ones in the OP (they don't have 14 lines), and I don't know what line 30 of your program does, I can only take a wild guess: Maybe $file2data{$columns1[0]} is empty, because the first columns of the files don't match up exactly. As stated, the example code doesn't really handle that case, but you could fairly easily modify it so it does, depending on what your input actually looks like. Without seeing a more representative sample of your input and your current program it's hard to say what the best solution is. See also the Basic debugging checklist.
In reply to Re^3: Adding some columns into a file from two files using perl
by Anonymous Monk
in thread Adding some columns into a file from two files using perl
by perlselami
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