The following code converts a piece of source code to HTML, highlighting the lines that have changed compared to a previous (unshown) version of the code. Call the code with two arguments like perl bolddiff.pl oldfile newfile to show newfiles with the files that have been added or changed since old bolded. 

#!perl

use warnings; use strict; use CGI;

1 == @ARGV || 2 == @ARGV or die "usage: perl bolddiff.pl file1 file2";
my $two = 2 <= @ARGV;
my ($f0n, $f1n) = @ARGV;
my $key = "BOLDDIFF_" . join("", map { int(rand(10)) } 0..5);
my $H;
if ($two) {
    open $H, "-|", "diff", "-bD", $key, "--", $f1n, $f0n or die;
} else {
    open $H, "<", $f0n or die;
}

print qq{<pre class="clisting">\n};
my $tap = 1; my $diff = 0;
while (<$H>) {
    if (/\b\Q$key\E\b/) {
        if (/\A#ifdef \Q$key\E\b/) {
            $tap = 0; $diff = 1;
        } elsif (/\A#ifndef \Q$key\E\b/) {
            $tap = 1; $diff = 1;
        } elsif (/\A#else \/\* \Q$key\E\b/) {
            $tap = !$tap;
        } elsif (/\A#endif \/\* (! )?\Q$key\E\b/) {
            $tap = 1; $diff = 0;
        } else {
            die "ifdef key unexpected: $_";
        }
    } else {
        if ($tap) {
            s/&/&amp;/g; s/</&lt;/g; s/>/&gt;/g;
            $diff and s/(.*)/<strong>$1<\/strong>/;
            print;
        }
    }
}
print qq{</pre>\n};

__END__

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In reply to Htmlify code with differences by ambrus

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


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