while (<>)
{
   $lines{$ARGV}++;
   ...
}

##</code><code>##

while (<ARGV>)
{
   if ( $ARGV ne $current_file )
   {
      print "\n","-" x 20, " $ARGV ", "-" x 20, "\n";
      $current_file = $ARGV;
      $files++;
   }
   print;
}