module ClockSkew ( clkin, clkout );
  timeunit 1ns;
  timeprecision 1ps;

  parameter DELAY_RTL = 0.0;
  parameter DELAY_GL = 0.0;

  input clkin;
  output clkout;

  reg clkskew;

  always @(*) begin
`ifdef GATE_LEVEL
     if (DELAY_GL > 0) clkskew = #DELAY_GL clkin ;
`else
     if (DELAY_RTL > 0) clkskew = #DELAY_RTL clkin ;
`endif
     else clkskew = clkin ;
  end

  assign clkout = clkskew ;

endmodule

...

ClockSkew #(.DELAY_RTL(0.0), .DELAY_GL(0.2)) ClockSkew (
  .clkout(ClockSkew_clkout),
  .clkin(ClockSkew_clkin))

In file included from /scratch/mikeyang/federation.gamma04/csrc/verilator-main.cpp:7:0:
./VTestDriver.h:337476:142: error: enumerator value for TestDriver__DOT__testHarness__DOT__ClockSkew__DOT__DELAY_RTL�� is not an integer constant
      enum _QDataTestDriver__DOT__testHarness__DOT__ClockSkew__DOT__DELAY_RTL { TestDriver__DOT__testHarness__DOT__ClockSkew__DOT__DELAY_RTL = 0.0};
                                                                                                                                               ^
./VTestDriver.h:337477:140: error: enumerator value for ��TestDriver__DOT__testHarness__DOT__ClockSkew__DOT__DELAY_GL�� is not an integer constant
      enum _QDataTestDriver__DOT__testHarness__DOT__ClockSkew__DOT__DELAY_GL { TestDriver__DOT__testHarness__DOT__ClockSkew__DOT__DELAY_GL = 2.00000000000000011e-01};
                                                                                                                                             ^