Thanks toolic,appreciate your help.the information was very useful. I am trying to do the following a)open the files in a given directory/subdirectories-only files with extension .v/.vh/.svn/.sv/.svi. At present concentrating on only .v and .vh b)search for verilog module definition c)for each module that is defined more than once the list of all files(full path /relative path) in which the module is defined should be printed. d)must be able to exclude // from parsing i figured out i could do much of the stuff using o the vhier,but i am unsure of how to use the verilog arguments like 1.+incdir+dir =item -Idir Add the directory to the list of directories that should be searched for include directories or libraries. 2.and also the vhier -f file:Read the specified file, and act as if all text inside it was specified as command line parameters. Should a filehandle be passed or just the filename? I know this sounds really silly asking such basic questions but I am good at writing perl code rather than using packages Would appreciate if you could throw some light on this. Thanks