SQL & PL/SQL :: Decode Functionality In DBMS_OUTPUT

I would like to use the below decode in DBMS_OUTPUT in place of cur_rec.data_type. Could I know how can I achieve this.
The DBMS_OUTPUT is inside a loop and output is shown below as an example.

NOT NULL -- EMP_ID NUMBER
,NOT NULL -- EMP_NAME NUMBER
,NOT NULL -- HIRE_DT DATE
,NOT NULL -- SALARY NUMBER

DBMS_OUTPUT STMT:

Dbms_Output.Put_Line(nullable ||CHR(9)||CHR(9)||' -- ' ||upper(cur_rec.column_name)||CHR(9)||CHR(9)||cur_rec.data_type);

STMT to use in place of cur_rec.data_type:

substr(decode( data_type, 'NUMBER', decode( data_precision, NULL, NULL,'('||data_precision||','||data_scale||')' ),data_length),1,11)

Also I am not able to align the output using CHR(9).