I like responses like yours, which take the OP's code and try to breathe some life into it. In particular, you take some aim at providing some data set to work off of, which is critical if OP wants others to replicate their post. One thing I like about usenet is that we tried to do that on threads. (One thing I don't like about usenet was the meanspiritness and increased domination by topic trolls. I let my subscription lapse.)

I did not see any difference in the 2 docs that pryrt's script produces. Everything seemed to be green. What follows are abridged output and then source:

 
$ ./1.excel.pl 
TUAROKUNSDSIG
JLUXOBCQYAIXDS
YAKB
...
UA
OJGFXQYPVIVO
UD
IABE
$ cat 1.excel.pl 
#!/usr/bin/perl -w

use 5.011;
use Spreadsheet::WriteExcel;

many_formats: {
    my $wb = Spreadsheet::WriteExcel->new('1.output_many.xls');
    my $sheet = $wb->add_worksheet("overview");
    foreach my $row (0..100) {
        local $\ = "\n";
        print my $line = join('', map { ('A'..'Z')[rand 26] } 0 .. ran
+d 16);
        my $header1 = $wb->add_format(bold=>0, color=>'green', size=>1
+0, merge=>0);
        $sheet->set_column(1,1,30);
        $sheet->write($row, 1, $line, $header1);
    }
    undef $wb;
}

shared_format: {
    my $wb = Spreadsheet::WriteExcel->new('1.output_shared.xls');
    my $header1 = $wb->add_format(bold=>0, color=>'green', size=>10, m
+erge=>0);
    my $sheet = $wb->add_worksheet("overview");
    foreach my $row (0..100) {
        local $\ = "\n";
        print my $line = join('', map { ('A'..'Z')[rand 26] } 0 .. ran
+d 16);
        $sheet->set_column(1,1,30);
        $sheet->write($row, 1, $line, $header1);
    }
    undef $wb;
}
__END__
[download]

My question is: given OP's script, what qualifies as a well-conditioned data set for this problem? OP says that his input is the output of a program: why is it unpostable between readmore tags?