WebPub helps install and manage popular web apps. We currently are doing WordPress, Drupal, MODX and phpBB. While the web UI is in PHP (decided before I came onboard) the backend is all Perl.

Some of the major components being used are: Mojolicious, Moose, DBIx::Class and Gearman.
Mojolicious provides the REST interface for the PHP front end and will be used in the near future by at least one other company we are working with. That company will write their client in Ruby.
Moose is used heavily for meta method creation, mapping various before / after 'method' to validation and DB update_or_create and the installer system loads the appropriate role (each app has its own role for things that are app specific - an install of Drupal needs more fixup than WP) at runtime.
DBIx::Class - no explaination needed
Gearman - actual interaction with remote systems happens from workers.