I believe you want to use the -y option instead of the +incdir+ option: 
$ ls i2c
i2c_master_top.v
$ vhier -y i2c --modules i2c_master_top.v
  i2c_master_top

[download]

The vhier command line is a lot like your favorite Verilog simulator command line. +incdir+ is used only when Verilog source code files include other source code files using the `include compiler directive.

Update: I thought this looked familiar: Re^4: verilog perl usage

In reply to Re: verilog-perl vhier usage by toolic
in thread verilog-perl vhier usage by Anonymous Monk

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