This lets you compare two csv files and choose which columns should be unique. The code isn't realy pretty but it was a quick hack and i though others might find it usefull. If nothing else now i'll be able to find ti agian if i loose it. ;)

#!/usr/bin/perl
use strict;
use warnings;
use Text::CSV;
use Data::Dumper;

my ($key, $file1, $file2) = (shift, shift,shift);
die "Usage: compare <keycol> <file1> <file2>\n"
            unless defined $file1 && defined $file2 && defined $key;

open( my $fh1, "<", $file1) or die "Failed to open '$file1'";
open( my $fh2, "<", $file2) or die "Failed to open '$file2'";

my $csv = Text::CSV->new;

my @key_cols = split ",", $key;
my @lines1 = <$fh1>;
my @lines2 = <$fh2>;

chomp @lines1;
chomp @lines2;

my ($hash1, $hash2, $hash_all);

for my $line (@lines1) {
   if ($csv->parse($line)) {
      my @field = $csv->fields;
      $key = "";$key .= "__" . uc($field[$_]) for @key_cols;
      $hash1->{$key} = @field;
      $hash_all->{$key} = $line;
   }
}

for my $line (@lines2) {
   if ($csv->parse($line)) {
      my @field = $csv->fields;
      $key = "";$key .= "__" . uc($field[$_]) for @key_cols;
      $hash2->{$key} = @field;
      $hash_all->{$key} = $line;
   }
}

for my $key (keys %$hash_all) {
    print "1,", $hash_all->{$key},"\n" unless exists $hash1->{$key};
    print "2,", $hash_all->{$key},"\n" unless exists $hash2->{$key};
}
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