[horde] mass-prefs update ?

[sCALP]

Hi, I'm sorry, I didn't found the answer elsewhere, but I want to ask 
before writing the tool from scratch.
I recently upgraded Horde/Imp from v2/v3 to v3/v4 and I had to change 
the 'folders' value of my servers.php config file from 'INBOX/' to '' 
(don't ask me why, I think I've done a mistake.... ;-)
so, the users close to me went to their options to change the folders 
path accordingly ('sent-mail' => 'INBOX.sent-mail', ....) but I want to 
do that globally for all my users.
is there a tool allowing me to update the prefs values for ALL users ?
I'm about to do this with a huge PHP/SQL/grep/replace, but if I can 
prevent me from doing this...
many thanks, and sorry if I bother with such a 'please help me correct 
my mistakes' question.
sincerely,
sCALP