#!/bin/perl5

use strict;
use warnings;
use HTML::TokeParser::Simple;

my $p = HTML::TokeParser::Simple->new(\*DATA);
my $http = q{http://domain.com};
while (my $t = $p->get_token){
  if (
    $t->is_start_tag(q{img})
      and
    $t->get_attr(q{src})
  )
  {
    my $src = $t->get_attr(q{src});
    if ($src !~ m|^http://|){
      $src = join '/', $http, $src;
      $t->set_attr(src => $src);
    }
  }
  print $t->as_is;
}

__DATA__
<img src="pics/local.jpg" alt="" />
<img src="http://remote.com/pics/remote.jpg" />
more confusion, just in case: 3:00pm 12/12/12
other urls <a href="http://fake.com">
http://fake.com</a>

##</code><code>##

<img src="http://domain.com/pics/local.jpg" alt="" />
<img src="http://remote.com/pics/remote.jpg" />
more confusion, just in case: 3:00pm 12/12/12
other urls <a href="http://fake.com">
http://fake.com</a>