#!/usr/bin/perl -w
use strict;

use Text::Tabs; # core module

die "Usage: real_diff.pl file.txt [file2.txt ..]\n"
    unless @ARGV;

my $prev_line;
my $file;

while(<>) {
    $file = $1 if /^RCS file: (.*?),/;
    if(/^.{62}[<>\|]/) {
        if(not $prev_line or $prev_line < $. - 1) {
            print "=" x 70, "\n";
            print "Line number in $ARGV.txt: $.\n";
            print "Source file name: $file\n\n";
        }
        print expand($_);
        $prev_line = $.;
    }
}