%Error-UNSUPPORTED: t/t_program_extern.v:7:1: Unsupported: extern program
    7 | extern program ex_pgm;
      | ^~~~~~
                    ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
%Error-UNSUPPORTED: t/t_program_extern.v:8:1: Unsupported: extern interface
    8 | extern interface ex_ifc;
      | ^~~~~~
%Error-UNSUPPORTED: t/t_program_extern.v:9:1: Unsupported: extern module
    9 | extern module ex_mod;
      | ^~~~~~
%Error: Exiting due to