sub parse_file ($) {
  #Do something with the file here.
}

sub traverse (@) {
  my @files = @_; 
  local *DIRH;

  #If @files is empty, why bother?
  return unless @files;

  foreach my $file (@files) {
    #Skip unreadable files.
    next unless -r $file;
    if (-d $file) {
      #If it's a directory ...
      chomp(my $cwd = system('/bin/pwd')); #save current directory, ...
      chdir($file) || next;                #change to the new directory, ...
      opendir(DIRH,$file) || next;         #open it...
      traverse((readdir(DIRH));            #and recursively parse it.
      closedir(DIRH);                      #Close the directory.
      chdir($cwd);                         #Change directories back to where we were.
    } else {
      #If it's not a directory, then parse it.
      parse_file($file);                    #This is where the actual work is done.
    }
  }
}

traverse(@ARGV);