Check the names of your worksheets, maybe you have leading spaces

#!usr/bin/perl
use strict;
use warnings;
use Spreadsheet::ParseExcel::SaveParser;

my $parser = Spreadsheet::ParseExcel::SaveParser->new();
my $xls = 'B_MUM_dashboard_month_latency_corrected_FDB.XLS';
my $wb = $parser->Parse($xls);
for ($wb->worksheets){
  print "'$_->{Name}'\n";
}
[download]