In answer to your first question, it isn't possible to put a newline in a Excel cell using the tab delimited format that you show. (Strangely, Excel will store a tab delimited file with this feature but doesn't read it back in correctly).

You can do it using a csv file by quoting cells that contain newlines, using only \n in the cell and \r\n for the end of line.

Here is an example:

    #!/usr/bin/perl -w

    use strict;
    use Text::CSV_XS;


    my @data = (
                 ["Hello,\nworld"  ],
                 ["One\nTwo\nThree"],
               );

    my $csv = Text::CSV_XS->new({binary => 1});


    open CSV, "> example.csv"  or die "Couldn't open file. $!\n";

    binmode CSV;

    for my $aref (@data) {

        $csv->combine(@$aref);
        print CSV $csv->string(), "\r\n";
    }
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(As an aside, anyone who recommends csv as an *easy* way of writing data to Excel should consider how arcane this example is).

Using Spreadsheet::WriteExcel you can can achieve this effect by specifying a text_wrap format:

    #!/usr/bin/perl -w

    use strict;
    use Spreadsheet::WriteExcel;

    my $workbook  = Spreadsheet::WriteExcel->new('example.xls');
    my $worksheet = $workbook->add_worksheet();

    my $format    = $workbook->add_format(text_wrap => 1);

    $worksheet->write('A1',  "Hello\nWorld", $format);
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See the following for other ways of writing Excel files.

--
John.