my %Columns = (
    'label' => {
        default => 0,
        exists => 0,
    },
    'key' => {
        default => 1,
        exists => 0,
    },
    'cross' => {
        default => 2,
        exists => 0,
    },
);

foreach my $col_name (keys %Columns)
{
    $Columns[$col_name}{exists} =
        column_exists( \@data, $_[1] || $Columns{$col_name}{default} );
    die if $Columns{$col_name}{exists} == -1;
}