You construct SCHEDULE_ROWS and SCHEDULE_COLUMNS in two different loops:

# SCHEDULE_ROWS
for my $dif_schedule(@schedule) 
{
    my %schedule_rows_data;
    $schedule_rows_data{SCHEDULE}=$dif_schedule;
    push (@schedule_rows_loop, \%schedule_rows_data); 
}

# SCHEDULE_COLUMNS
for(my $i=0;$i<=$scheduled_export_days;$i++)
{
    my %schedule_columns_data;
    $schedule_columns_data{SCHEDULE_COLUMNS_COUNT}=1;
    push (@schedule_columns_loop, \%schedule_columns_data);
}

# ...later
$data_structure{SCHEDULE_ROWS} = \@schedule_rows_loop;
$data_structure{SCHEDULE_COLUMNS} =\@schedule_columns_loop;
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For your table to work, SCHEDULE_COLUMNS needs to be a key within SCHEDULE_ROWS, so you need to construct it within the first loop, but without knowing your actual data I can't tell how to do that.