( $filePrefix_In, @entries_In, $yr_ref, $mth_ref, $dt_ref )  = @_ ;

$yr_ref and the following variables will never get any values here, because all rest values from @_ are slurped into @entries_In. Either re-order your arguments, or use an array reference, or pass a hash of all values (including an array reference) around.

Please start all your perl scripts with

use strict;
use warnings;
[download]

I think it would have caught that error.

Also

print Dumper @fileName   ;

is much more informative if you write print Dumper \@fileName; instead.