I don't think that setting $. will help you much. This variable is incremented on each read, but it isn't used by perl to track its place in the file. In fact, $. isn't even file specific. I quote from the Camel Book,

The current input line number of the last filehandle that was read. An explicit close on the filehandle resets the line number. Since <> never does an explicit close, line numbers increase across ARGV files