Actually I've got a login, but sometimes I refrain because monks will get annoyed at how many times I post a question...lol. Anyway, please tell me where you get lost in my post so I can get better at writing these situations.

Now, let me explain in detail what's happening.

@data is read from a file containg many rows such as:
1,comp1,type1
2,comp2,type2
3,comp3,type3

@data2 is read from a file containing many rows such as:
1,comp1,type1,doc1,ref1
2,comp2,type2,doc2,ref2
3,comp3,type3,doc3,ref3
4,comp4,type4,doc4,ref4
5,comp5,type5,doc5,ref5

Using this code:

{
    my %data;
    undef @data{@data};
    foreach ( @data2 ) {
        print "This $_ was not found.\n"
            if not exists $data{$_}
    }
}
[download]

it matches all five values from each line in @data2 to all 3 values in @data line by line. So basically every line in @data2 gets printed when that script is run. What I want to do is match the first value from @data2 to the first value from @data and return the results based on values in @data2 that are not in @data.

I also want to know how I can match the second value from @data2 to the first value in @data and return the results that are not in @data.

I hope this makes better senses. I'll keep trying if it doesn't. Thanks for all your help.