Mariachi, the not really Siesta bit

 % cpanp --prereqs i Mariachi

time passes

 % time mariachi -i threadtest -o london.pm --name london.pm
 reticulating splines                               0.000 elapsed 0.000 total
 load 37                                            0.434 elapsed 0.434 total
 dropped 0 duplicate messages
 dedupe                                             0.007 elapsed 0.441 total
 thread                                             0.042 elapsed 0.483 total
 sanity                                             0.010 elapsed 0.493 total
 order                                              0.010 elapsed 0.503 total
 sanity                                             0.008 elapsed 0.511 total
 copy files                                         0.110 elapsed 0.621 total
 tt init                                            0.078 elapsed 0.699 total
 lurker output                                      0.998 elapsed 1.697 total
 strand                                             0.009 elapsed 1.705 total
 splicing threads in 1 places
 deep threads split up                              0.010 elapsed 1.716 total
 sanity                                             0.008 elapsed 1.724 total
 order                                              0.011 elapsed 1.734 total
 regular thread indexes                             0.270 elapsed 2.004 total
 date indexes                                       0.263 elapsed 2.267 total
 messages                                           1.928 elapsed 4.195 total

You'll have a london.pm folder, not unlike this one