There is one thing I would mention. Gtk2 has the Plug and Socket concept, which I never could get to work..... but, google for "gtk+ plug socket". Perl/Gtk2 has methods to use plugs and sockets.

If you could find a word processor that was written in GTK+, you may be able to use plug/socket with it from Perl/Gtk2.

If you do get it going, please write a tutorial on it. ;-) The Perl/Gtk2 maillist would be a good place to ask.