This means that $template was not initialized properly. Check the return value of

my $template = $parser->Parse('B_MUM_dashboard_month_latency_corrected
+_FDB.XLS');
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like this

my $filename = 'B_MUM_dashboard_month_latency_corrected_FDB.XLS';
my $template = $parser->Parse($filename)
    or die "Couldn't read '$filename': " . $parser->error;
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That way, you find out why your template was not initialized properly.