#! perl
use strict;
use warnings;
use Excel::Writer::XLSX;
use Spreadsheet::BasicRead;

my $workbook  = Excel::Writer::XLSX->new('perl.xlsx') or die "$!";
my $worksheet = $workbook->add_worksheet(); 
my @files     = ('data.xlsx');

foreach my $file (@files)
{
    my $excel = new Spreadsheet::BasicRead($file) or die "$!";
    my $row   = 0;

    while (my $dataref = $excel->getNextRow())
    {
        foreach my $date (@$dataref[7 .. 8])  # Columns H and I
        {
            $date =~ s[ ^ (\d{1,2}) / (\d{1,2}) / (\d{4}) $  ]
                      [ sprintf("%4d-%02d-%02d", $3, $2, $1) ]ex;
        }

        $worksheet->write_row($row++, 0, $dataref);
    }
}

##</code><code>##

1.1	2.1	3.3	4.4	5.5	6.6	7.7	9/15/2012	7/18/1960	8.8	9.9

##</code><code>##

1.1	2.1	3.3	4.4	5.5	6.6	7.7	2012-15-09	1960-18-07	8.8	9.9