#!perl
use strict;
use Win32::OLE;

$Win32::OLE::Warn = 3; # die on errors
my $file = 'c:\\temp\\Book1.xml';

my $Excel = Win32::OLE->GetActiveObject('Excel.Application')
         || Win32::OLE->new('Excel.Application');

my $workbook = $Excel->Workbooks->Open($file);

$workbook->saveAs('c:\\temp\\Book1.xlsx',{FileFormat => 51}); #xlWorkbookDefault
$workbook->Close();
$Excel->Quit();