As chilledham points out it is Excel that is converting the number to a floating point format.

The way to avoid this (in Excel and Spreadsheet::WriteExcel) is to specify a cell format to ensure that the number is displayed in the way you want. You will also need to add some link style formatting to ensure it also looks like a link. Here is a working example:

#!/usr/bin/perl

use warnings;
use strict;
use Spreadsheet::WriteExcel;

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

my $link_format = $workbook->add_format(
    color      => 'blue',
    underline  => 1,
    num_format => 1,
);

$worksheet->set_column( 'B:B', 20 );

$worksheet->write_url( 'A1', 'www.perl.com', 270751343164, $link_forma
+t );
$worksheet->write_url( 'B1', 'www.perl.com', 270751343164, $link_forma
+t );

__END__
[download]

The set_column() method call is there to show how to display the number since it is now larger than the cell.