Not sure why perl-generated spreadsheet has formatting issues

[poopay]

I have recently created a perl script that aims to collect information from different spreadsheets and combine the data into one spreadsheet.

I've set 2 columns to display data in a date format. The spreadsheet was indeed generated; however, I noticed that the date in the formatted column treat the dates as string.

However, I noticed that if I double-click the cell with the dates then press "Enter", the data is then converted to the format I wanted it to be.

This is a snippet of the code I created

 
#create your destination spreadsheet
my $workbook = Excel::Writer::XLSX->new( 'perl.xlsx' );
my $worksheet = $workbook->add_worksheet(); 

#set date format for rows H and I
my $format = $workbook->add_format( num_format => 'yyyy-mm-dd' );

#create some formatting for dates
$worksheet->set_column('H:I', undef, $format);

# for every spreadsheet...
foreach $file (@files)
{
    do
    {
        #Read the input file        
        $excel = new Spreadsheet::BasicRead($file);
        
        #Get the data from each row        
        while ($dataref = $excel->getNextRow())
        {
            #Write the data into your destination spreadsheet and incr
+ement row
            my @data = @$dataref;
            $worksheet->write_row($row, 0, \@data);
            $row++;
        
        }
    }
}

Is there a way for my output to be displayed properly in the correct format without me doing this? Hope someone can help.