What charset does Microsoft Excel use when saving files

#!perl

use strict;

use Spreadsheet::ParseExcel::Simple;
use Encode qw( decode );

my $file    = "my_spreadsheet.xls";

my $xls     = Spreadsheet::ParseExcel::Simple->read( $file );
my $sheet   = [ $xls->sheets ]->[0];

while ($sheet->has_data) {

    my @data = $sheet->next_row;

    for my $datum ( @data ) {
        print decode( 'cp1250', $datum );
    }

}