There have already been lots of good answers, but since i had already thrown this together, here it is for whatever value it might be. Cheers.

sub process_file {
        my ($hash, $file) = @_;
        open my $fh, "<", $file or die $!;
        while (<$fh>) {
                chomp;
                my ($target, @columns) = split /,/;
                $hash->{$target}[0] = $target;
                for my $c (0 .. $#columns) {
                        $hash->{$target}[$c+1] .= $columns[$c];
                }
        }
        close $fh;
}

$, = ',';
print ("Now merging \n");
my $data = {};
process_file($data, $_) for glob("*.csv");
say @{$data->{$_}} for sort keys %$data;
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