Read in my first input line and store it in $oldline
Now loop over the rest of the input lines
   if the current line is the same as $oldline, then
      increment our count
   otherwise (that is, the current line is different)
      print $oldline and the counter
      reset the counter
      set the current line as the next line to keep track of by storing it in $oldline
Loop
if there's something in $oldline (which will always be the case), print it