$.      The current input line number of the last filehandle
             that  was  read.   Readonly.   Remember that only an
             explicit close on the  filehandle  resets  the  line
             number.  Since <> never does an explicit close, line
             numbers increase across ARGV files (but see examples
             under  eof).  (Mnemonic: many programs use . to mean
             the current line number.)