If your data should be ordered, than you simply use an multidimensional array over a hash:

my @reports = (
    [doc_request => [qw(T_Doc_Request N_Doc_Request X_Doc_Request)]],
    [doc_errors  => [qw(T_Doc_Errors  N_Doc_Errors  X_Doc_Errors )]],
    [doc_types   => [qw(T_Doc_Types   N_Doc_Errors  X_Doc_Errors )]],
);

for (@reports) {
    my $report = $_->[0];
    for my $section (@{$_->[1]}) {
        print qq{report '$report', section '$section'\n};
    }
}
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