use strict;
my $excel = 'c:/Programs/Microsoft Office/Excel/excel.exe';
my $file = "c:\\path\\to\\my test.xls";
# note that Excel might want the filename delimited
# with backslashes
system( $excel, $file ) == 0
  or die "Couldn't start Excel: $^E / $! / $?";

##</code><code>##

use strict;
my $file = "c:\\path\\to\\my test.xls";
# note that cmd.exe wants the filename delimited
# with backslashes
system( 'start', $file );

##</code><code>##

use strict;
use Win32::OLE;

my $excel = Win32::OLE->new( 'Excel.Application' );
my $file = "c:\\path\\to\\my test.xls";

$excel->Open( $file );
# or so I believe. Use the Macro Recorder to find out
# what the function names are actually called