Well if you don't have mod_perl installed (as stated in the original question), you won't be writing code as a handler, and also won't be tying the output to Apache.

Try this in a 'normal' CGI script:

#!/usr/bin/perl -w

print "Content-disposition: attachment;filename=test.xls\n";
print "Content-type: application/vnd.ms-excel\n\n";

binmode(STDOUT);
my $workbook  = Spreadsheet::WriteExcel->new('-');
my $worksheet = $workbook->addworksheet();
$worksheet->write("A1","Hello, World");
$workbook->close;
[download]