The function that you need is FmtString() which is a method of the Spreadsheet::ParseExcel::FmtDefault class.

Here is a short example which assumes that there is formatted data in cell A1 of the first worksheet:

    #!/usr/bin/perl -w

    use strict;
    use Spreadsheet::ParseExcel;
    use Spreadsheet::ParseExcel::FmtDefault;

    my $file     = Spreadsheet::ParseExcel->new();
    my $format   = Spreadsheet::ParseExcel::FmtDefault->new();
    my $workbook = $file->Parse('test.xls');


    my ($row, $col) = (0, 0);
    my $worksheet   = $workbook->{Worksheet}[0];
    my $cell        = $worksheet->{Cells}[$row][$col];

    print $format->FmtString($cell, $workbook), "\n";
[download]

You could also consider the Spreadsheet::ParseExcel::SaveParser part of Spreadsheet::ParseExcel which can be used to update an existing Excel file. The following is an example from the pod of the newer simplified interface.

    use strict;
    use Spreadsheet::ParseExcel::SaveParser;
    $oBook = 
        Spreadsheet::ParseExcel::SaveParser::Workbook->Parse('Test97.x
+ls');
    my $oWs = $oBook->AddWorksheet('TEST1');
    $oWs->AddCell(10, 1, 'New Cell');
    $oBook->SaveAs('iftest.xls');
[download]

--
John.