while ( <> ) {
...
elsif ( s|http://www.theirsite.com/\W|http://our.server1/theirsite/\n|i ){ }
elsif ( s|http://www.theirsite.com/|http://our.server1/theirsite/|i ) { }
elsif ( s|http://www.dummy.com/\W|http://our.server2/dummy/\n|i ) { }

# .. ad nauseam
}