All of the VITO tools use a parser compatible with the original (1995) version of the Verilog standard (IEEE 1364). The grammar for this language is roughly described here:
http://www.verilog.com/VerilogBNF.html
Although the implicit style subset used in later Verilog standards (2001 and 2005) is completely compatible with this, the additional features these later Verilog standards (and the similar SystemVerilog IEEE 1800 standard) introduce may cause VITO tools to flag source code using these features as syntax errors.