correct line numbers

runoff1

@@ -13,12 +13,15 @@ if($ARGV[0] eq "-n") {
 }
 $n = int(($n+49)/50)*50 - 1;
 
+$file = $ARGV[0];
 @lines = <>;
+$linenum = 0;
 foreach (@lines) {
+	$linenum++;
 	chomp;
 	s/\s+$//;
 	if(length() >= 75){
-		print "$ARGV[0]:$.: line too long";
+		print STDERR "$file:$linenum: line too long\n";
 	}
 }
 @outlines = ();