P:\test>type junk.txt
http://www.theirsite.com/
http://www.dummy.com/
http://www.theirsite.com/stuff
http://www.dummy.com/stuff
http://www.theirsite.com/ stuff
http://www.dummy.com/ stuff

P:\test>perl 324406-2.pl < junk.txt
$VAR1 = {
          'www.theirsite.com' => 'our.server1/theirsite/',
          'www.dummy.com' => 'our.server2/dummy/'
        };

http://our.server1/theirsite/
http://our.server2/dummy/
http://our.server1/theirsite/
stuff
http://our.server2/dummy/
stuff
http://our.server1/theirsite/ stuff
http://our.server2/dummy/ stuff